StudioWelcome: Add get() to ProjectModel

This is required for compatibility with ListModel.

Change-Id: I7bb738b1f5c54d9f49cf0fa30dc65940f7645bb6
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/studiowelcome/studiowelcomeplugin.cpp

@@ -92,6 +92,11 @@ public:
         ProjectExplorer::ProjectExplorerPlugin::openProjectWelcomePage(projectFile);
     }
 
+    Q_INVOKABLE int get(int)
+    {
+        return -1;
+    }
+
     Q_INVOKABLE void showHelp()
     {
         QDesktopServices::openUrl(QUrl("qthelp://org.qt-project.qtcreator/doc/index.html"));