Fatal error: Call to a member function overrideCollectionPermissions() on a non-object

Permalink
This morning, a user deleted some files from File Manager and renamed a couple stacks. The website is now producing this error:
Fatal error: Call to a member function overrideCollectionPermissions() on a non-object in /homepages/31/d404075293/htdocs/updates/concrete5.6.3.4/concrete/core/models/permission/assignments/area.php on line 33

I tried reverting to the older stacks and deleting the renamed stacks. I updated from 5.6.3.1 to 5.6.3.4. The error persists on all pages. I don't have a database backup.

Any other ideas? Otherwise I'm thinking we may have lost the site.