While trying to commit a sub-module, I was prompted to enter my username and email address. When I click OK, the prompt comes right back. When I click cancel, the commit window stays on screen, but I can't do anything. If I click the commit dialog box, the prompt for password comes back.

This leaves the UI in a dead end state, the only way to recover is to force quit SourceTree and restart. Pressing the escape key does not help, and using the quit menu option just causes a beep.

See the attached animated GIF.