Prevent window close if user choose cancel in quit window

main/ui/src/main/java/org/cryptomator/ui/mainwindow/MainWindowTitleController.java

@@ -59,6 +59,7 @@ public class MainWindowTitleController implements FxController {
 		});
 		window.setOnCloseRequest(event -> {
 			close();
+			event.consume();
 		});
 	}