Fix ScreenSaver problem.

src/main.cpp

@@ -46,6 +46,7 @@ int main(int argc, char* argv[])
 
 
     UsctApplication a(argc, argv);
+    qRegisterMetaType<QPair<QString, uint>>("QPair<QString, uint>");
     QString layouts_path = QString(QCoreApplication::applicationDirPath()).append("/layouts");
     qputenv("QT_VIRTUALKEYBOARD_LAYOUT_PATH", QByteArray(layouts_path.toStdString().c_str()));