fix some issues with qtfred's ship list dialog (#7329)

Author: MjnMixael

code/object/waypoint.cpp

@@ -433,7 +433,7 @@ void waypoint_stuff_name(SCP_string &dest, const char *waypoint_list_name, int w
 		return;
 	}
 
-	dest.assign(waypoint_list_name, name_max_len);
+	dest.assign(waypoint_list_name, std::min(strlen(waypoint_list_name), name_max_len));
 	dest += ":";
 	dest.append(std::to_string(waypoint_num));
 }

qtfred/src/mission/dialogs/SelectionDialogModel.cpp

@@ -51,7 +51,7 @@ void SelectionDialogModel::initializeData() {
 		entry.id = i;
 		entry.selected = false;
 
-		_wing_list.push_back(entry);
+		_waypoint_list.push_back(entry);
 	}
 }
 void SelectionDialogModel::updateObjectList() {

qtfred/src/ui/dialogs/SelectionDialog.cpp

@@ -107,16 +107,13 @@ void SelectionDialog::objectSelectionChanged() {
 	auto current = _model->getObjectList(); // Copy the vector so we can change the selection
 
 	for (auto& entry : current) {
-		auto items =
-			ui->shipSelectionList->model()->match(ui->shipSelectionList->model()->index(0, 0), Qt::UserRole, entry.id);
-
-		Assertion(items.size() > 0, "No items for object index found!");
-		Assertion(items.size() <= 1, "Found multiple items for one object index!");
-
-		auto item = ui->shipSelectionList->item(items[0].row());
-
-		Assertion(item != nullptr, "Couldn't find item for index!");
-		entry.selected = item->isSelected();
+		for (int row = 0; row < ui->shipSelectionList->count(); ++row) {
+			auto* item = ui->shipSelectionList->item(row);
+			if (item->data(Qt::UserRole).value<int>() == entry.id) {
+				entry.selected = item->isSelected();
+				break;
+			}
+		}
 	}
 
 	_model->updateObjectSelection(current);