SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: SELECT t.*, t.boardid AS bid FROM bb1_threads t WHERE t.threadid =
mysql error: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 1
mysql error number: 1064
mysql version: 10.5.19-MariaDB-0+deb11u2-log
php version: 5.6.40
Date: 26.09.2023 @ 20:24
Script: /hoerspiele.php?action=easysearch_result&syn=Lutz+Mackensy
Referer: