Adding an object type attribute with empty Default type caused attribute UI not loading

Issue Summary

This is reproducible on Data Center: N/A

Steps to Reproduce

1. Select an object type and go to its object type attribute view.
2. Add a new attribute. Select Default as 'Type' and clear the content of 'Type Value'.
3. Click 'Add' button. Refresh the page.

Expected Results

No attribute was added. UI should force customer to select a 'Type Value'.

Actual Results

An abnormal attribute was added which caused the attribute view not loading.

Workaround

No obvious workaround.

Update the default type value from database and restart the instance can resolve the issue.