[BUG] Cancelling dive planning from keyboard

[Miika Turkia]

Hello,

I played around with the dive planner a bit on taxi and discovered a
bug. When I cancel the dive planning from keyboard, the dive is not
deleted (as when clicking the cancel button with mouse).

Steps to reproduce:
- Open dive planner
- Insert depth for first segment
- tab to next field
- insert time
- tab to next field - at this point the dive appears in the divelist
* hit either esc or ctrl-c
=> The planner is closed but dive remains on the divelist

At first glance the delete_single_dive is called properly with correct
parameters, but apparently something is still not right. It is also
notable that if you tab until on the next depth field, the delete from
keyboard succeeds...

miika