MySQL error in file: /engine/modules/show.full.php at line 985

Error Number: 3685

The Error returned was:
Illegal argument to a regular expression.

SQL query:

SELECT id, date, short_story, xfields, title, category, alt_name FROM dle_post WHERE category regexp '[[:<:]](7)[[:>:]]' AND MATCH (title, short_story, full_story, xfields) AGAINST ('Undertale ') AND id != 8934 AND approve=1 AND date < '2025-03-15 07:48:03' LIMIT 5