Creating a document type with the same name fails without error msg

When I create a new document type, if I use the same name as an existing document type, the dialog closes without an error message.

Reproduction:

1. Log in to cms as admin
2. Go to configuration accordian
3. Create new document type
4. Use "newsdocument" as name (in archetype)

Expected: an error message

Observed: Dialog closes, no new doc type