On attempting to manage the theme from site settings and save, I receive the following error:

"Call to undefined method Cms\Classes\Theme::fill()" on line 92 of /Users/bryansaltzman/www/valetsites/neatquiz/modules/backend/traits/FormModelSaver.php

Any ideas? It seems a basic array is being passed into the function instead of a October\Rain\Database\Model.

I can't replicate this error. I can save changes on theme settings without any issue.

Are there any errors when you run composer update on your installation?