handle case where the login fails because the user doesn't exist

Author: tomschlick

src/AuthNotifications.php

@@ -38,6 +38,10 @@ public function handleFailed(Failed $event): void
         if (! in_array($event->guard, config('auth-notifications.listen_to.login_failed.guards'))) {
             return;
         }
+        
+        if (empty($event->user)) {
+            return;
+        }
 
         $event->user->notify(new LoginFailed($event, request()));
     }