Bug description

If the User opens the new registration window via the welcome window by pressing 'continue', and then closes it, the application will lose focus and keyboard users won't be able to close or re-enter the window.

Steps to reproduce

1. Open Audaicty
2. Observe welcome dialog window
3. Press 'Continue' on audio.com slidee
4. Close the regsitration window
5. Try to tab around
6. Observe result

Expected behavior

The focus should be switched back to the welcome window after registration dialog has been closed.

Actual behavior

The focus is not switched back to the welcome window after registration dialog has been closed.

Audacity Version

ba024db

Operating system

OS independent

Additional context