MySQL error in file: /engine/modules/show.short.php at line 65

Error Number: 1139

The Error returned was:
Got error 'empty (sub)expression' from regexp

SQL query:

SELECT p.id, p.autor, p.date, p.short_story, CHAR_LENGTH(p.full_story) as full_story, p.xfields, p.title, p.category, p.alt_name, p.comm_num, p.allow_comm, p.fixed, p.tags, e.news_read, e.allow_rate, e.rating, e.vote_num, e.votes, e.view_edit, e.editdate, e.editor, e.reason FROM dle_post p LEFT JOIN dle_post_extras e ON (p.id=e.news_id) WHERE category regexp '[[:<:]](|166|163|164|165)[[:>:]]' AND approve=1 AND date < '2022-08-15 10:30:34' ORDER BY fixed desc, date DESC LIMIT 0,10