Error adding multiple airlines without IATA codes

[barf]

Describe the bug
An error occurs when adding multiple airlines that are sans/without IATA codes specified.

Version
git dev branch

To Reproduce
Steps to reproduce the behavior:

1. Install phpVMS on Ubuntu using Apache with MariaDB
2. Complete installation and configure the first airline without an IATA code.
3. Add an additional airline without an IATA code
4. See error

Expected behavior
Airline is added

Additional context
Output from storage/logs/lavarel-.log

[2020-05-03 07:31:39] prod.ERROR: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'airlines_iata_unique' (SQL: insert into `airlines` (`icao`, `name`, `iata`, `logo`, `country`, `active`, `updated_at`, `created_at`) values (40SQN, 40 Squadron, , ?, nz, 1, 2020-05-03 07:31:37, 2020-05-03 07:31:37)) {"userId":4,"exception":"[object] (Illuminate\\Database\\QueryException(code: 23000): SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'airlines_iata_unique' (SQL: insert into `airlines` (`icao`, `name`, `iata`, `logo`, `country`, `active`, `updated_at`, `created_at`) values (40SQN, 40 Squadron, , ?, nz, 1, 2020-05-03 07:31:37, 2020-05-03 07:31:37)) at /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php:669)
[stacktrace]
#0 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(629): Illuminate\\Database\\Connection->runQueryCallback()
#1 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(464): Illuminate\\Database\\Connection->run()
#2 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(416): Illuminate\\Database\\Connection->statement()
#3 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Query/Processors/Processor.php(32): Illuminate\\Database\\Connection->insert()
#4 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Query/Builder.php(2695): Illuminate\\Database\\Query\\Processors\\Processor->processInsertGetId()
#5 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Builder.php(1366): Illuminate\\Database\\Query\\Builder->insertGetId()
#6 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(840): Illuminate\\Database\\Eloquent\\Builder->__call()
#7 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(805): Illuminate\\Database\\Eloquent\\Model->insertAndSetId()
#8 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(668): Illuminate\\Database\\Eloquent\\Model->performInsert()
#9 /var/www/phpvms-git/vendor/prettus/l5-repository/src/Prettus/Repository/Eloquent/BaseRepository.php(632): Illuminate\\Database\\Eloquent\\Model->save()
#10 /var/www/phpvms-git/app/Services/AirlineService.php(40): Prettus\\Repository\\Eloquent\\BaseRepository->create()
#11 /var/www/phpvms-git/app/Http/Controllers/Admin/AirlinesController.php(66): App\\Services\\AirlineService->createAirline()
#12 [internal function]: App\\Http\\Controllers\\Admin\\AirlinesController->store()
#13 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Controller.php(54): call_user_func_array()
#14 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(45): Illuminate\\Routing\\Controller->callAction()
#15 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Route.php(219): Illuminate\\Routing\\ControllerDispatcher->dispatch()
#16 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Route.php(176): Illuminate\\Routing\\Route->runController()
#17 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(681): Illuminate\\Routing\\Route->run()
#18 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(130): Illuminate\\Routing\\Router->Illuminate\\Routing\\{closure}()
#19 /var/www/phpvms-git/vendor/santigarcor/laratrust/src/Middleware/LaratrustAbility.php(51): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#20 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Laratrust\\Middleware\\LaratrustAbility->handle()
#21 /var/www/phpvms-git/vendor/santigarcor/laratrust/src/Middleware/LaratrustAbility.php(51): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#22 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Laratrust\\Middleware\\LaratrustAbility->handle()
#23 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Middleware/SubstituteBindings.php(41): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#24 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Routing\\Middleware\\SubstituteBindings->handle()
#25 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Auth/Middleware/Authenticate.php(43): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#26 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Auth\\Middleware\\Authenticate->handle()
#27 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/View/Middleware/ShareErrorsFromSession.php(49): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#28 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\View\\Middleware\\ShareErrorsFromSession->handle()
#29 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(56): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#30 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Session\\Middleware\\StartSession->handle()
#31 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php(37): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#32 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Cookie\\Middleware\\AddQueuedCookiesToResponse->handle()
#33 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php(66): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#34 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Cookie\\Middleware\\EncryptCookies->handle()
#35 /var/www/phpvms-git/app/Http/Middleware/InstalledCheck.php(29): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#36 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): App\\Http\\Middleware\\InstalledCheck->handle()
#37 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(105): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#38 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(683): Illuminate\\Pipeline\\Pipeline->then()
#39 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(658): Illuminate\\Routing\\Router->runRouteWithinStack()
#40 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(624): Illuminate\\Routing\\Router->runRoute()
#41 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(613): Illuminate\\Routing\\Router->dispatchToRoute()
#42 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(170): Illuminate\\Routing\\Router->dispatch()
#43 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(130): Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}()
#44 /var/www/phpvms-git/vendor/barryvdh/laravel-debugbar/src/Middleware/InjectDebugbar.php(58): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#45 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Barryvdh\\Debugbar\\Middleware\\InjectDebugbar->handle()
#46 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#47 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#48 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#49 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#50 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode.php(63): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#51 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\CheckForMaintenanceMode->handle()
#52 /var/www/phpvms-git/app/Http/Middleware/TrustProxies.php(38): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#53 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): App\\Http\\Middleware\\TrustProxies->handle()
#54 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(105): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#55 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(145): Illuminate\\Pipeline\\Pipeline->then()
#56 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(110): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter()
#57 /var/www/phpvms-git/public/index.php(23): Illuminate\\Foundation\\Http\\Kernel->handle()
#58 {main}

[previous exception] [object] (Doctrine\\DBAL\\Driver\\PDOException(code: 23000): SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'airlines_iata_unique' at /var/www/phpvms-git/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOStatement.php:119)
[stacktrace]
#0 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(463): Doctrine\\DBAL\\Driver\\PDOStatement->execute()
#1 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(662): Illuminate\\Database\\Connection->Illuminate\\Database\\{closure}()
#2 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(629): Illuminate\\Database\\Connection->runQueryCallback()
#3 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(464): Illuminate\\Database\\Connection->run()
#4 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Connection.php(416): Illuminate\\Database\\Connection->statement()
#5 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Query/Processors/Processor.php(32): Illuminate\\Database\\Connection->insert()
#6 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Query/Builder.php(2695): Illuminate\\Database\\Query\\Processors\\Processor->processInsertGetId()
#7 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Builder.php(1366): Illuminate\\Database\\Query\\Builder->insertGetId()
#8 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(840): Illuminate\\Database\\Eloquent\\Builder->__call()
#9 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(805): Illuminate\\Database\\Eloquent\\Model->insertAndSetId()
#10 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(668): Illuminate\\Database\\Eloquent\\Model->performInsert()
#11 /var/www/phpvms-git/vendor/prettus/l5-repository/src/Prettus/Repository/Eloquent/BaseRepository.php(632): Illuminate\\Database\\Eloquent\\Model->save()
#12 /var/www/phpvms-git/app/Services/AirlineService.php(40): Prettus\\Repository\\Eloquent\\BaseRepository->create()
#13 /var/www/phpvms-git/app/Http/Controllers/Admin/AirlinesController.php(66): App\\Services\\AirlineService->createAirline()
#14 [internal function]: App\\Http\\Controllers\\Admin\\AirlinesController->store()
#15 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Controller.php(54): call_user_func_array()
#16 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(45): Illuminate\\Routing\\Controller->callAction()
#17 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Route.php(219): Illuminate\\Routing\\ControllerDispatcher->dispatch()
#18 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Route.php(176): Illuminate\\Routing\\Route->runController()
#19 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(681): Illuminate\\Routing\\Route->run()
#20 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(130): Illuminate\\Routing\\Router->Illuminate\\Routing\\{closure}()
#21 /var/www/phpvms-git/vendor/santigarcor/laratrust/src/Middleware/LaratrustAbility.php(51): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#22 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Laratrust\\Middleware\\LaratrustAbility->handle()
#23 /var/www/phpvms-git/vendor/santigarcor/laratrust/src/Middleware/LaratrustAbility.php(51): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#24 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Laratrust\\Middleware\\LaratrustAbility->handle()
#25 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Middleware/SubstituteBindings.php(41): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#26 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Routing\\Middleware\\SubstituteBindings->handle()
#27 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Auth/Middleware/Authenticate.php(43): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#28 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Auth\\Middleware\\Authenticate->handle()
#29 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/View/Middleware/ShareErrorsFromSession.php(49): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#30 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\View\\Middleware\\ShareErrorsFromSession->handle()
#31 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(56): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#32 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Session\\Middleware\\StartSession->handle()
#33 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php(37): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#34 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Cookie\\Middleware\\AddQueuedCookiesToResponse->handle()
#35 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php(66): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#36 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Cookie\\Middleware\\EncryptCookies->handle()
#37 /var/www/phpvms-git/app/Http/Middleware/InstalledCheck.php(29): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#38 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): App\\Http\\Middleware\\InstalledCheck->handle()
#39 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(105): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#40 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(683): Illuminate\\Pipeline\\Pipeline->then()
#41 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(658): Illuminate\\Routing\\Router->runRouteWithinStack()
#42 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(624): Illuminate\\Routing\\Router->runRoute()
#43 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Routing/Router.php(613): Illuminate\\Routing\\Router->dispatchToRoute()
#44 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(170): Illuminate\\Routing\\Router->dispatch()
#45 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(130): Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}()
#46 /var/www/phpvms-git/vendor/barryvdh/laravel-debugbar/src/Middleware/InjectDebugbar.php(58): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#47 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Barryvdh\\Debugbar\\Middleware\\InjectDebugbar->handle()
#48 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#49 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#50 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#51 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#52 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode.php(63): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#53 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\CheckForMaintenanceMode->handle()
#54 /var/www/phpvms-git/app/Http/Middleware/TrustProxies.php(38): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#55 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): App\\Http\\Middleware\\TrustProxies->handle()
#56 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(105): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#57 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(145): Illuminate\\Pipeline\\Pipeline->then()
#58 /var/www/phpvms-git/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(110): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter()
#59 /var/www/phpvms-git/public/index.php(23): Illuminate\\Foundation\\Http\\Kernel->handle()
#60 {main}