Dont go balls on new thread post.

misago/threads/views/posting.py

@@ -164,8 +164,9 @@ class PostingView(BaseView):
                 # Create new message
                 if self.mode in ['new_thread', 'new_post', 'new_post_quick']:
                     # Use last post instead?
-                    merge_diff = (now - self.thread.last)
-                    merge_diff = (merge_diff.days * 86400) + merge_diff.seconds
+                    if self.mode in ['new_post', 'new_post_quick']:
+                        merge_diff = (now - self.thread.last)
+                        merge_diff = (merge_diff.days * 86400) + merge_diff.seconds
                     if (self.mode in ['new_post', 'new_post_quick']
                         and request.settings.post_merge_time
                         and merge_diff < (request.settings.post_merge_time * 60)