MySQL error in file: /engine/cache/system/plugins/2018fbbc2fc1e65994f8cdbc28665f4e.php at line 709

Error Number: 3685

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

SQL query:

SELECT count(*) as count FROM dle_post where approve=1 and category regexp '[[:<:]](9|13)[[:>:]]'