[nostalgia/core/studio] Fix ng export to only attempt export if output file is given

src/nostalgia/core/studio/tilesheeteditor.cpp

@@ -461,13 +461,14 @@ TileSheetEditor::~TileSheetEditor() {
 	saveState();
 }
 
-QString TileSheetEditor::itemName() {
+QString TileSheetEditor::itemName() const {
 	return m_itemName;
 }
 
 void TileSheetEditor::exportFile() {
 	auto path = QFileDialog::getSaveFileName(this, tr("Export to Image"), "",
 	                                         tr("PNG (*.png)"));
+	if (path != "") {
 		auto ng = m_sheetData.toNostalgiaGraphic();
 		QString palPath;
 		if (palPath == "" && ng->defaultPalette.type() == ox::FileAddressType::Path) {
@@ -482,6 +483,7 @@ void TileSheetEditor::exportFile() {
 		}
 		toQImage(ng.get(), npal.get()).save(path, "PNG");
 	}
+}
 
 void TileSheetEditor::saveItem() {
 	m_sheetData.save(m_ctx, m_itemPath);