Error upgrading admin module to version 1.7

The admin panel had a notice to automatically upgrade to test version 1.7.

I clicked upgrade, and now when accessing the admin panel it throws the following exception:

RuntimeException (500)
Cannot load blueprint blueprints://flex-objects/pages.yaml: Invalid resource theme://

Error is thrown from:


How do I fix it? Is there a module I must enable or disable? Is there a way to rollback to the previous stable version?