Check for array content before querying keys in Worker\Notifier
Check for array content before querying keys in Worker\Notifier

- Address https://github.com/friendica/friendica/issues/11218#issuecomment-1045137358

friendica/friendica,annando/friendica,friendica/friendica,annando/friendica,annando/friendica,friendica/friendica,friendica/friendica,friendica/friendica,annando/friendica,annando/friendica