Don't enter edit profile mode when already editing the dive

This is not the ideal solution. Ideally we might want to simply enter the
profile edit mode if we edit a dive that was manually added. But right now
the code contains lots of assumptions about being in one mode or the other
and as we are redoing the profile / planner classes for 4.1 anyway, I'd
rather err on the safe side for 4.0.1

Fixes #374

(well, it fixes the second bug reported in 374 which is quite different
from the original bug)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>