SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: DELETE FROM bb1_adminsessions WHERE userid=0 AND lastactivity<1547994827
mysql error: Can't find file: './DB69620/bb1_adminsessions.frm' (errno: 13)
mysql error number: 1017
mysql version: 5.1.41-3ubuntu12.7
php version: 4.4.9
Date: 20.01.2019 @ 16:03
Script: /blexer/wbb2/addreply.php
Referer: