MapEditorController: Remove Popup window for empty map parts

If the map part to be removed or merged is empty, it's an option to
avoid asking the user before removing the empty map part as no objects
are affected.
This commit removes the popup window in case of empty map parts.

src/gui/map/map_editor.cpp

@@ -3850,42 +3850,41 @@ void MapEditorController::addMapPart()
 void MapEditorController::removeMapPart()
 {
 	auto* part = map->getCurrentPart();
-	auto i = part->getNumObjects();
+	auto num_objects = part->getNumObjects();
 
-	QMessageBox::StandardButton button =
-	        QMessageBox::question(
-	            window,
+	if (num_objects > 0)
+	{
+		if (QMessageBox::question(
+                window,
                 tr("Remove current part"),
-                i ? tr("Do you want to remove map part \"%1\" and its %2 objects?").arg(part->getName()).arg(i) :
-                    tr("Do you want to remove empty map part \"%1\"?").arg(part->getName()),
-                QMessageBox::Yes | QMessageBox::No );
+                tr("Do you want to remove map part \"%1\" and its %2 objects?").arg(part->getName()).arg(num_objects),
+                QMessageBox::Yes | QMessageBox::No ) == QMessageBox::No)
+		return;
+	}
 
-	if (button == QMessageBox::Yes)
+	auto index = map->getCurrentPartIndex();
+	UndoStep* undo_step = new MapPartUndoStep(map, MapPartUndoStep::AddMapPart, index);
+
+	if (num_objects > 0)
 	{
-		auto index = map->getCurrentPartIndex();
-		UndoStep* undo_step = new MapPartUndoStep(map, MapPartUndoStep::AddMapPart, index);
-
-		if (i > 0)
+		auto* add_step = new AddObjectsUndoStep(map);
+		do
 		{
-			auto* add_step = new AddObjectsUndoStep(map);
-			do
-			{
-				--i;
-				auto* object = part->getObject(i);
-				add_step->addObject(i, object);
-				part->releaseObject(object);
-			}
-			while (i > 0);
-
-			auto* combined_step = new CombinedUndoStep(map);
-			combined_step->push(add_step);
-			combined_step->push(undo_step);
-			undo_step = combined_step;
+			--num_objects;
+			auto* object = part->getObject(num_objects);
+			add_step->addObject(num_objects, object);
+			part->releaseObject(object);
 		}
+		while (num_objects > 0);
 
-		map->push(undo_step);
-		map->removePart(index);
+		auto* combined_step = new CombinedUndoStep(map);
+		combined_step->push(add_step);
+		combined_step->push(undo_step);
+		undo_step = combined_step;
 	}
+
+	map->push(undo_step);
+	map->removePart(index);
 }
 
 void MapEditorController::renameMapPart()
@@ -3936,33 +3935,34 @@ void MapEditorController::mergeCurrentMapPartTo(int target)
 {
 	MapPart* const source_part = map->getCurrentPart();
 	MapPart* const target_part = map->getPart(target);
-	const QMessageBox::StandardButton button =
-	        QMessageBox::question(
-	            window,
-                tr("Merge map parts"),
-                tr("Do you want to move all %1 objects from map part \"%2\" to \"%3\", "
-	               "and to remove \"%2\"?")
-	            .arg(source_part->getNumObjects()).arg(source_part->getName(), target_part->getName()),
-                QMessageBox::Yes | QMessageBox::No );
+	auto num_objects = source_part->getNumObjects();
 
-	if (button == QMessageBox::Yes)
+	if (num_objects > 0)
 	{
-		// Beware that the source part is removed, and
-		// the target part's index might change during merge.
-		auto source = map->getCurrentPartIndex();
-		UndoStep* add_part_step = new MapPartUndoStep(map, MapPartUndoStep::AddMapPart, source);
-
-		auto first  = map->mergeParts(source, target);
-
-		auto* switch_part_undo = new SwitchPartUndoStep(map, target, source);
-		for (auto i = target_part->getNumObjects(); i > first; --i)
-			switch_part_undo->addObject(0);
-
-		auto* undo = new CombinedUndoStep(map);
-		undo->push(switch_part_undo);
-		undo->push(add_part_step);
-		map->push(undo);
+		if (QMessageBox::question(
+	            window,
+                tr("Merge map parts"),
+                tr("Do you want to move all %1 objects from map part \"%2\" to \"%3\", and to remove \"%2\"?")
+                  .arg(num_objects).arg(source_part->getName(), target_part->getName()),
+                QMessageBox::Yes | QMessageBox::No ) == QMessageBox::No)
+		return;
 	}
+
+	// Beware that the source part is removed, and
+	// the target part's index might change during merge.
+	auto source = map->getCurrentPartIndex();
+	UndoStep* add_part_step = new MapPartUndoStep(map, MapPartUndoStep::AddMapPart, source);
+
+	auto first  = map->mergeParts(source, target);
+
+	auto* switch_part_undo = new SwitchPartUndoStep(map, target, source);
+	for (num_objects = target_part->getNumObjects(); num_objects > first; --num_objects)
+		switch_part_undo->addObject(0);
+
+	auto* undo = new CombinedUndoStep(map);
+	undo->push(switch_part_undo);
+	undo->push(add_part_step);
+	map->push(undo);
 }
 
 void MapEditorController::mergeAllMapParts()