Type Error in the log (this issue title will be updated once the bug has be identified)

[marc-farre]

@PrimozRatej I've received errors in the log after your tests on https://demo.cuzy.app/

Could you provide more information about the way to reproduce this bug? Thanks!

URL: /fcm-push/token/update-mobile-app

Error log:

TypeError: humhub\modules\fcmPush\services\TokenService::storeTokenForUser(): Argument #3 ($token) must be of type string, null given, called in /var/www/humhub/protected/modules/fcm-push/controllers/TokenController.php on line 60 and defined in /var/www/humhub/protected/modules/fcm-push/services/TokenService.php:25
Stack trace:
#0 /var/www/humhub/protected/modules/fcm-push/controllers/TokenController.php(60): humhub\modules\fcmPush\services\TokenService->storeTokenForUser(Object(humhub\modules\user\models\User), Object(humhub\modules\fcmPush\driver\Proxy), NULL)
#1 [internal function]: humhub\modules\fcmPush\controllers\TokenController->actionUpdateMobileApp()
#2 /var/www/humhub/protected/vendor/yiisoft/yii2/base/InlineAction.php(57): call_user_func_array(Array, Array)
#3 /var/www/humhub/protected/vendor/yiisoft/yii2/base/Controller.php(178): yii\base\InlineAction->runWithParams(Array)
#4 /var/www/humhub/protected/vendor/yiisoft/yii2/base/Module.php(552): yii\base\Controller->runAction('update-mobile-a...', Array)
#5 /var/www/humhub/protected/vendor/yiisoft/yii2/web/Application.php(103): yii\base\Module->runAction('fcm-push/token/...', Array)
#6 /var/www/humhub/protected/vendor/yiisoft/yii2/base/Application.php(384): yii\web\Application->handleRequest(Object(humhub\components\Request))
#7 /var/www/humhub/index.php(25): yii\base\Application->run()
#8 {main}