Undefined error being displayed when saving a metadata source with Element Type = clientSecretRef

Scenario:

1. From the 'Add New' dropdown menu in the header, select 'Add a new metadata source'.
2. Select OIDC (OpenID Connect) from the Identity Protocol field.
3. Populate the Service Provider Name (Dashboard Display Only) and Entity ID fields.
4. Click on the 'Common Attributes' Next button.
5. Click on the 'User interface / MDUI Information' Next button.
6. Click on the 'SP SSO Descriptor Information' Next button.
7. Click on the 'Logout Endpoints' Next button.
8. Click on the 'Security Information' Next button.
9. Select the true radio button for both 'Authentication Requests Signed?' and 'Want Assertions Signed?'.
10. Click the 'Add +' button for Key Descriptors.
11. Populate the 'Certificate Name (Display Only)' field.
12. Select clientSecretRef from the 'Element Type' dropdown menu.
13. Select the 'signing' radio button.
14. Populate the Value field.
15. Click on the 'Assertion Consumer Service' Next button.
16. Click on the 'Relying Party Overrides' Next button.
17. Click on the 'Attributes Release' Next button.
18. Click on the 'Finish' Next button.
19. Click the Save button.

Expected behavior: The metadata resource is saved.

Actual behavior: An undefined error is displayed.