Undefined index InteractiveTreeModule - dev system

[makitso]

I have seen this error in the webtrees log for quite some time but never posted it.

Apache Log:
17.121.112.25 - - [15/Nov/2021:07:18:27 -0800] "GET /module/tree/Chart/peters HTTP/1.1" 500 52125 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1.1 Safari/605.1.15 (Applebot/0.1; +http://www.apple.com/go/applebot)"

webtrees log: 2021-11-15 15:18:28

Undefined index: xref …/app/Module/InteractiveTreeModule.php:192 #0 …/app/Module/InteractiveTreeModule.php(192): Fisharebest\Webtrees\Webtrees::Fisharebest\Webtrees{closure}() #1 …/app/Http/RequestHandlers/ModuleAction.php(87): Fisharebest\Webtrees\Module\InteractiveTreeModule->getChartAction() #2 …/app/Http/Middleware/RequestHandler.php(55): Fisharebest\Webtrees\Http\RequestHandlers\ModuleAction->handle() #3 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\RequestHandler->process() #4 …/app/Http/Middleware/CheckCsrf.php(75): Middleland\Dispatcher->handle() #5 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\CheckCsrf->process() #6 …/vendor/oscarotero/middleland/src/Dispatcher.php(118): Middleland\Dispatcher->handle() #7 …/app/Webtrees.php(241): Middleland\Dispatcher->dispatch() #8 …/app/Http/Middleware/Router.php(149): Fisharebest\Webtrees\Webtrees::dispatch() #9 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\Router->process() #10 …/app/Http/Middleware/BootModules.php(60): Middleland\Dispatcher->handle() #11 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\BootModules->process() #12 …/app/Http/Middleware/LoadRoutes.php(74): Middleland\Dispatcher->handle() #13 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\LoadRoutes->process() #14 …/app/Http/Middleware/UseTransaction.php(45): Middleland\Dispatcher->handle() #15 …/vendor/illuminate/database/Concerns/ManagesTransactions.php(29): Fisharebest\Webtrees\Http\Middleware\UseTransaction::Fisharebest\Webtrees\Http\Middleware{closure}() #16 …/app/Http/Middleware/UseTransaction.php(46): Illuminate\Database\Connection->transaction() #17 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UseTransaction->process() #18 …/app/Http/Middleware/DoHousekeeping.php(73): Middleland\Dispatcher->handle() #19 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\DoHousekeeping->process() #20 …/app/Http/Middleware/UseTheme.php(69): Middleland\Dispatcher->handle() #21 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UseTheme->process() #22 …/app/Http/Middleware/CheckForMaintenanceMode.php(51): Middleland\Dispatcher->handle() #23 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\CheckForMaintenanceMode->process() #24 …/app/Http/Middleware/UseLanguage.php(69): Middleland\Dispatcher->handle() #25 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UseLanguage->process() #26 …/app/Http/Middleware/UseSession.php(75): Middleland\Dispatcher->handle() #27 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UseSession->process() #28 …/app/Http/Middleware/UpdateDatabaseSchema.php(57): Middleland\Dispatcher->handle() #29 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UpdateDatabaseSchema->process() #30 …/app/Http/Middleware/UseDebugbar.php(67): Middleland\Dispatcher->handle() #31 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UseDebugbar->process() #32 …/app/Http/Middleware/UseDatabase.php(117): Middleland\Dispatcher->handle() #33 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\UseDatabase->process() #34 …/app/Http/Middleware/BadBotBlocker.php(226): Middleland\Dispatcher->handle() #35 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\BadBotBlocker->process() #36 …/app/Http/Middleware/CompressResponse.php(73): Middleland\Dispatcher->handle() #37 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\CompressResponse->process() #38 …/app/Http/Middleware/ContentLength.php(40): Middleland\Dispatcher->handle() #39 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\ContentLength->process() #40 …/vendor/middlewares/client-ip/src/ClientIp.php(65): Middleland\Dispatcher->handle() #41 …/app/Http/Middleware/ClientIp.php(47): Middlewares\ClientIp->process() #42 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\ClientIp->process() #43 …/app/Http/Middleware/HandleExceptions.php(89): Middleland\Dispatcher->handle() #44 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\HandleExceptions->process() #45 …/app/Http/Middleware/BaseUrl.php(77): Middleland\Dispatcher->handle() #46 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\BaseUrl->process() #47 …/app/Http/Middleware/ReadConfigIni.php(68): Middleland\Dispatcher->handle() #48 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\ReadConfigIni->process() #49 …/app/Http/Middleware/SecurityHeaders.php(48): Middleland\Dispatcher->handle() #50 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\SecurityHeaders->process() #51 …/app/Http/Middleware/EmitResponse.php(57): Middleland\Dispatcher->handle() #52 …/vendor/oscarotero/middleland/src/Dispatcher.php(136): Fisharebest\Webtrees\Http\Middleware\EmitResponse->process() #53 …/vendor/oscarotero/middleland/src/Dispatcher.php(118): Middleland\Dispatcher->handle() #54 …/app/Webtrees.php(241): Middleland\Dispatcher->dispatch() #55 …/app/Webtrees.php(228): Fisharebest\Webtrees\Webtrees::dispatch() #56 …/index.php(44): Fisharebest\Webtrees\Webtrees->httpRequest() #57 {main}