Prefer `update!` -> `update!`.

lib/post_destroyer.rb

@@ -167,7 +167,7 @@ class PostDestroyer
   def make_previous_post_the_last_one
     last_post = Post.where("topic_id = ? and id <> ?", @post.topic_id, @post.id).order('created_at desc').limit(1).first
     if last_post.present?
-      @post.topic.update_attributes(
+      @post.topic.update!(
         last_posted_at: last_post.created_at,
         last_post_user_id: last_post.user_id,
         highest_post_number: last_post.post_number