Error: Call to a member function update() on null

[fey]

Error: Call to a member function update() on null
  File "/app/vendor/laracasts/flash/src/Laracasts/Flash/FlashNotifier.php", line 112
  File "/app/vendor/laracasts/flash/src/Laracasts/Flash/FlashNotifier.php", line 92, in Laracasts\Flash\FlashNotifier::updateLastMessage
  File "/app/vendor/laracasts/flash/src/Laracasts/Flash/FlashNotifier.php", line 66, in Laracasts\Flash\FlashNotifier::message
  File "/app/app/Http/Controllers/Auth/Social/GithubController.php", line 89, in Laracasts\Flash\FlashNotifier::error
  File "/app/app/Http/Controllers/Auth/Social/GithubController.php", line 44, in App\Http\Controllers\Auth\Social\GithubController::sendFailedResponse
  File "unknown", line unknown, in App\Http\Controllers\Auth\Social\GithubController::handleProviderCallback
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Controller.php", line 54, in call_user_func_array
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php", line 45, in Illuminate\Routing\Controller::callAction
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Route.php", line 239, in Illuminate\Routing\ControllerDispatcher::dispatch
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Route.php", line 196, in Illuminate\Routing\Route::runController
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Router.php", line 685, in Illuminate\Routing\Route::run
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 128, in Illuminate\Routing\Router::Illuminate\Routing\{closure}
  File "/app/vendor/mcamara/laravel-localization/src/Mcamara/LaravelLocalization/Middleware/LaravelLocalizationRedirectFilter.php", line 45, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Mcamara\LaravelLocalization\Middleware\LaravelLocalizationRedirectFilter::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Middleware/SubstituteBindings.php", line 41, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Routing\Middleware\SubstituteBindings::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/VerifyCsrfToken.php", line 77, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Foundation\Http\Middleware\VerifyCsrfToken::handle
  File "/app/vendor/laravel/framework/src/Illuminate/View/Middleware/ShareErrorsFromSession.php", line 49, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\View\Middleware\ShareErrorsFromSession::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php", line 116, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php", line 62, in Illuminate\Session\Middleware\StartSession::handleStatefulRequest
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Session\Middleware\StartSession::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php", line 37, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php", line 67, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Cookie\Middleware\EncryptCookies::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 103, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Router.php", line 687, in Illuminate\Pipeline\Pipeline::then
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Router.php", line 662, in Illuminate\Routing\Router::runRouteWithinStack
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Router.php", line 628, in Illuminate\Routing\Router::runRoute
  File "/app/vendor/laravel/framework/src/Illuminate/Routing/Router.php", line 617, in Illuminate\Routing\Router::dispatchToRoute
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php", line 165, in Illuminate\Routing\Router::dispatch
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 128, in Illuminate\Foundation\Http\Kernel::Illuminate\Foundation\Http\{closure}
  File "/app/vendor/fideloper/proxy/src/TrustProxies.php", line 57, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Fideloper\Proxy\TrustProxies::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php", line 21, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Foundation\Http\Middleware\TransformsRequest::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php", line 21, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Foundation\Http\Middleware\TransformsRequest::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ValidatePostSize.php", line 27, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Foundation\Http\Middleware\ValidatePostSize::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode.php", line 63, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 167, in Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::handle
  File "/app/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php", line 103, in Illuminate\Pipeline\Pipeline::Illuminate\Pipeline\{closure}
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php", line 140, in Illuminate\Pipeline\Pipeline::then
  File "/app/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php", line 109, in Illuminate\Foundation\Http\Kernel::sendRequestThroughRouter
  File "/app/public/index.php", line 55, in Illuminate\Foundation\Http\Kernel::handle