Error on node type save

Howdy,

Applied #3 patch, and error is gone.

the issue is that we use the same validation callback for node and node_type forms.
We should create two separate callbacks to fix it (already implemented as a part of the issue - https://www.drupal.org/project/custom_body_class/issues/3055694 🐛 No dependency on the Node type class module Needs review )

Created a new MR.

Added two validation callbacks for node and node type forms.