Files_antivirus NextCloud 12?

Tell and how it is correct to adjust files_antivirus on Nextcloud 12? In additions I included it, in the administrator’s panel of setup appeared. I tried everything, but he does not check for viruses in any way, and in a log

Error PHP preg_match (): Delimiter must not be alphanumeric or backslash at /var/www/nextcloud/apps/files_antivirus/lib/Status.php#80
Error PHP Undefined variable: rule at /var/www/nextcloud/apps/files_antivirus/controller/rulecontroller.php#107

Also in a log information on verification of the uploaded files is not displayed. And still wanted to learn and how to adjust the notification on email about the found virus?

Is installed on the server:

Ubuntu 16.04
Nextcloud 12.0.2 stable
files_antivirus taken with Github