Explicitly store UI values to prefs

This helper wasn't called as intended - but because of the syncSettings
call which emits settingsChanged this only became visible for the
default_filename.

Next I need to clean up what is called for the settingsChanged signal.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Rewrite readSettings to do what it should have done from the start

This function was supposed to take the default_prefs into account but
clearly wasn't.

Now it should be much more readable and maintainable.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Stop showing the first dive after a preferences change

What is missing is the code to actually show the RIGHT dive...

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Update the current dive when no dive was selected

The check to only update the dive if there were already dives selected
before seems bogus. I'm sure I put it there for a reason but it seems
flat out wrong.

This gets triggered when you select a trip by clicking on the trip
header. In that case all dives get unselected (amount_selected = 0) and
then we try to select the first dive in the trip - which fails because
of this check.

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