Add remind user to execute empty scan.

src/windows/MainWindow.h

@@ -53,6 +53,8 @@ private:
     void loadStyleSheet(const QString& aSheetName);
     void showShutdownWidget();
     void processShutdownDmsFailed();
+    void checkEmptyScanValidity();
+    void enableAllTabWidget();
 
 private:
     Ui::MainWindow* mUI;