ARR: Comment threshold thread ID for deleted replies

[haroldrubio]

Some of the the replyto fields of all current replies may not be present (as in they may have been deleted) and causes the thread ID to resolve incorrectly, assume orphaned comments belong to the forum thread

def get_thread_id(tree, comment_id, forum):
        thread_id = comment_id
        try:
            while tree[thread_id] != forum:
                thread_id = tree[thread_id]
        except KeyError:
            return forum
        return thread_id