Fixes showing the Empty Profile when Add / Plan dive is cancelled.

for some reason the next selected dive is NULL after cancelling the
plan. I'm investigating.

This patch fixes the show of the empty profile and it also untangles
some parts of the code, keeping the mainwindow where it should belong
: the mainwindow.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>