Error when used in combination webform_civirules

Using a Webform is submitted trigger throws the following error:

Error: Class name must be a valid object or a string in /var/www/html/sites/default/files/civicrm/ext/civirules/CRM/Civirules/Engine.php on line 303

That makes the webform_civirules useless

Cause: recent execution logging is added. The logging code makes the assumption that the underlying table is a CiviCRM table, and has a DOA class. For the webform_civirules no such table exists.