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>

qt-ui/mainwindow.cpp

@@ -65,7 +65,7 @@ void MainWindow::refreshDisplay()
 
 void MainWindow::current_dive_changed(int divenr)
 {
-	if (amount_selected && divenr >= 0) {
+	if (divenr >= 0) {
 		select_dive(divenr);
 		ui->globe->centerOn(get_dive(selected_dive));
 		redrawProfile();