Email notification error?

Hi,

After upgraded to NC11 from 10.0.2, my server has too much issues.
I have the same setup & settings, but NC11 giving me a lot of errors.

Error files_antivirus OCA\Files_Antivirus\BackgroundScanner::run, exception: File with id "6" has not been found.

    Error while running background job (Doctrine\DBAL\Exception\SyntaxErrorException): An exception occurred while executing 'DELETE FROM `oc_activity_mq` WHERE `amq_timestamp` <= ? AND `amq_affecteduser` IN ()' with params [1481756401]: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1
OCA\Activity\BackgroundJob\EmailNotification ):
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php - line 128: Doctrine\DBAL\Driver\AbstractMySQLDriver->convertException('An exception oc...', Object(Doctrine\DBAL\Driver\PDOException))
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Statement.php - line 178: Doctrine\DBAL\DBALException driverExceptionDuringQuery(Object(Doctrine\DBAL\Driver\PDOMySql\Driver), Object(Doctrine\DBAL\Driver\PDOException), 'DELETE FROM `oc...', Array)
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/apps/activity/lib/MailQueueHandler.php - line 334: Doctrine\DBAL\Statement->execute(Array)
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/apps/activity/lib/BackgroundJob/EmailNotification.php - line 131: OCA\Activity\MailQueueHandler->deleteSentItems(Array, 1481756401)
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/apps/activity/lib/BackgroundJob/EmailNotification.php - line 81: OCA\Activity\BackgroundJob\EmailNotification->runStep(500, 1481756401)
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/lib/private/BackgroundJob/Job.php - line 53: OCA\Activity\BackgroundJob\EmailNotification->run(NULL)
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/lib/private/BackgroundJob/TimedJob.php - line 54: OC\BackgroundJob\Job->execute(Object(OC\BackgroundJob\JobList), Object(OC\Log))
/media/54bf67db-da31-4c50-bb3c-27140944b223/www/nextcloud/cron.php - line 121: OC\BackgroundJob\TimedJob->execute(Object(OC\BackgroundJob\JobList), Object(OC\Log))
{main}

I found the solution MySQL error: https://github.com/nextcloud/server/issues/2688