Create content panel shows infinite progress bar trying to create a document with unknown validator

Scenario:

1. Add to any field of a document "unknown" validator.
2. Using "+" orange button try to create the document with 'unknown' validator.

Problem: Create content panel shows infinite progress bar trying to create a document with unknown validator.

Expected: needs a decision. One of the variants could be showing the message in Create Content panel step 2 with the link to Content perspective.