Steps to reproduce

1. Create a new job.
2. Select Subversion SCM
3. Click 'Add' next to credential selection of first module location. Notice that popup opens.
4. Close popup.
5. Click 'Add module...' or 'Add additional credentials...'
6. Click 'Add' next to credential selection of newly added form controls

Expected result
Popup opens

Actual result
Nothing happens

Notes
even color-on-hover and pressed state while clicking don't work for these buttons.

No messages logged in console.