Fix various OTP editing errors

[firecat53]

1. When the key is contained in the path as key=xxxxxxx instead of in the otp attribute as secret=xxxxx, editing will fail (edit.py line 200-202)
2. Hitting escape when asked for the Secret Key settings crashes (edit.py line 253):
   • UnboundLocalError: cannot access local variable 'time_step_choice' where it is not associated with a value