Fix saving vote for post/discussion created by deleted user (#145)

Author: rob006

src/Listeners/SaveVotesToDatabase.php

@@ -96,7 +96,7 @@ public function handle(Saving $event)
         }
     }
 
-    public function vote(Post $post, bool $isDownvoted, bool $isUpvoted, User $actor, User $user)
+    public function vote(Post $post, bool $isDownvoted, bool $isUpvoted, User $actor, ?User $user)
     {
         $vote = Vote::build($post, $actor);