Fix AvatarChanged event (#2197)

* Fix AvatarChanged event not being dispatched when changing avatar
Also fix the uploader to trigger the event only once

src/User/Command/UploadAvatarHandler.php

@@ -80,6 +80,8 @@ class UploadAvatarHandler
 
         $user->save();
 
+        $this->dispatchEventsFor($user, $actor);
+
         return $user;
     }
 }