Error 500 after call to notification URL

{"message":"Uncaught PHP Exception Symfony\\Component\\HttpKernel\\Exception\\ControllerDoesNotReturnResponseException: \"The controller must return a \"Symfony\\Component\\HttpFoundation\\Response\" object but it returned null. Did you forget to add a return statement somewhere in your controller?\" at /opt/quadramoula/quadramoula/src/Controller/Front/DonationController.php line 105","context":{"exception":{"class":"Symfony\\Component\\HttpKernel\\Exception\\ControllerDoesNotReturnResponseException","message":"The controller must return a \"Symfony\\Component\\HttpFoundation\\Response\" object but it returned null. Did you forget to add a return statement somewhere in your controller?","code":0,"file":"/opt/quadramoula/quadramoula/src/Controller/Front/DonationController.php:105"}},"level":500,"level_name":"CRITICAL","channel":"request","datetime":"2024-04-21T20:02:47.379772+02:00","extra":{}}