WCF::destruct() Unhandled exception: SQLSTATE[70100]: <>: 1927 Connection was killed

#0 /var/www/wbb/wcf/lib/data/DatabaseObjectEditor.class.php(68): wcf\system\database\Database->prepareStatement('UPDATE\twcf1_ses...')
#1 /var/www/wbb/wcf/lib/data/acp/session/ACPSessionEditor.class.php(42): wcf\data\DatabaseObjectEditor->update(Array)
#2 /var/www/wbb/wcf/lib/system/session/SessionHandler.class.php(866): wcf\data\acp\session\ACPSessionEditor->update(Array)
#3 /var/www/wbb/wcf/lib/system/WCF.class.php(175): wcf\system\session\SessionHandler->update()
#4 [internal function]: wcf\system\WCF::destruct()
#5 {main}