When pressing Return on the "New Session" screen, it would still try to unlock the session as the text field still has focus.
Instead of duplicating some logic there, just "click" the button which will do the right thing in both cases.

Locked screen, typed password, pressed Return, session unlocked.
Locked screen, choose "New Session", pressed Return, new session would be created (previously it would try to unlock, or do nothing if you didn't type anything before)