App still crashes on Rest = 0

[waij]

You solved issue #7 by not allowing setting Rest = 0. This is problematic for several reasons.

1. I consider repeated countdown without rest to be a valid use case.
2. The rest period can still be set to zero, crashing the app.
3. If you attempt to enter Rest = 0, the Rest field will remain empty. You can still start the timer. It crashes immediately.

Scenario for item 2:

• start the interval timer
• set Active = 5, Rest = 10
• edit the value 10 by removing the 1, leaving the number 0 as the value
• start the timer
• timer runs as expected in cycles of 5 seconds
• stop the timer

• the rest field is now empty (this is unexpected behavior)

• start the timer

• the timer crashes

For completeness: the app also crashes with Active = 0 and Rest = 1.