Duo "Client secret" field validation is inconsistent between creating and updating an MFA method.

Steps to reproduce:

1. Edit an existing Duo MFA method.
2. Press "Change client secret".
3. Leave the field empty.
4. Press "Update".

Result:
The field is not validated in the modal window (see animation):

Expected:
The field is validated in the popup window, same as when creating a new Duo method: