Error going to page 2 of search

hello, when I search for 'contact form' in the 'search by forum' and I click on page 2 I get the following error:

Got error 'empty (sub)expression' from regexp
SELECT SQL_CALC_FOUND_ROWS SQL_CALC_FOUND_ROWS topic_id as id, name, title, UNIX_TIMESTAMP(last_date) as ago, last_user, solution, users.nick as starter, (SELECT COUNT(*) FROM forum_posts WHERE topic_id = id) as posts, priority FROM forum_topics, users WHERE users.user_id = forum_topics.owner_id AND forum_topics.deleted = 0 AND title RLIKE '' ORDER BY priority, last_date DESC LIMIT 30, 30

Hi!

Could you give us the URL of your website, please.