Don't ignore equipment just because the dive list is empty

This was a fun little bug. Tomaz pointed me in the right direction. The UI
restructure with the displayed_dive had another unintended side effect
here. It is not valid not to set up the widgets just because the dive_list
is empty. The displayed_dive isn't on the dive_list until it is saved - so
while the user is adding or planning a dive, we still need to show the
equipment widgets.

Fixes #614
Fixes #601

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