FIX: be more lenient when creating a post with a username that is no longer valid

lib/post_creator.rb

@@ -267,11 +267,13 @@ class PostCreator
   end
 
   def update_topic_stats
-    # Update attributes on the topic - featured users and last posted.
-    attrs = {last_posted_at: @post.created_at, last_post_user_id: @post.user_id}
-    attrs[:bumped_at] = @post.created_at unless @post.no_bump
-    attrs[:word_count] = (@topic.word_count || 0) + @post.word_count
+    attrs = {
+      last_posted_at: @post.created_at,
+      last_post_user_id: @post.user_id,
+      word_count: (@topic.word_count || 0) + @post.word_count,
+    }
     attrs[:excerpt] = @post.excerpt(220, strip_links: true) if new_topic?
+    attrs[:bumped_at] = @post.created_at unless @post.no_bump
     @topic.update_attributes(attrs)
   end
 
@@ -331,8 +333,7 @@ class PostCreator
 
     @user.user_stat.save!
 
-    @user.last_posted_at = @post.created_at
-    @user.save!
+    @user.update_attributes(last_posted_at: @post.created_at)
   end
 
   def publish