code cleanup: introduce empty_cylinder constant

This deals with the issue of initializing structs in C++.

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

qt-models/cylindermodel.cpp

@@ -421,7 +421,7 @@ int CylindersModel::rowCount(const QModelIndex&) const
 void CylindersModel::add()
 {
 	int row = rows;
-	cylinder_t cyl = { 0 };
+	cylinder_t cyl = empty_cylinder;
 	fill_default_cylinder(&displayed_dive, &cyl);
 	cyl.start = cyl.type.workingpressure;
 	cyl.manually_added = true;

qt-models/diveplannermodel.cpp

@@ -166,12 +166,12 @@ void DivePlannerPointsModel::setupCylinders()
 		}
 	}
 	if (!empty_string(prefs.default_cylinder)) {
-		cylinder_t cyl = { 0 };
+		cylinder_t cyl = empty_cylinder;
 		fill_default_cylinder(&displayed_dive, &cyl);
 		cyl.start = cyl.type.workingpressure;
 		add_to_cylinder_table(&displayed_dive.cylinders, 0, cyl);
 	} else {
-		cylinder_t cyl = { 0 };
+		cylinder_t cyl = empty_cylinder;
 		// roughly an AL80
 		cyl.type.description = copy_qstring(tr("unknown"));
 		cyl.type.size.mliter = 11100;

qt-models/divetripmodel.cpp

@@ -515,7 +515,7 @@ void processRangesZip(Vector1 &items1, Vector2 &items2, Predicate cond, Action a
 			return 1;
 		      },
 		      [&](Vector1 &v1, int from, int to) { // Action
-		      	return action(v1, items2, from, to, actItem);
+			return action(v1, items2, from, to, actItem);
 		      });
 }
 
@@ -653,7 +653,7 @@ QModelIndex DiveTripModelTree::parent(const QModelIndex &index) const
 }
 
 DiveTripModelTree::Item::Item(dive_trip *t, const QVector<dive *> &divesIn) : d_or_t{nullptr, t},
-	dives(divesIn.toStdVector()),
+	dives(std::vector<dive *>(divesIn.begin(), divesIn.end())),
 	shown(std::any_of(dives.begin(), dives.end(), [](dive *d){ return !d->hidden_by_filter; }))
 {
 }