SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: SELECT m.*, m.userid AS moderatorid,b.* FROM bb1_boards b LEFT JOIN bb1_moderators m ON (m.boardid=b.boardid AND m.userid='0') WHERE b.boardid = '45'
mysql error: Can't open file: './usr_web1_2/bb1_moderators.frm' (errno: 24)
mysql error number: 1016
mysql version: 5.5.47-0+deb6u1-log
php version: 5.3.3-7+squeeze29
Date: 05.07.2020 @ 10:17
Script: /board.php?boardid=45&daysprune=1000&sortfield=lastposttime&sortorder=ASC
Referer: