Cocoa: Adding a ApplicationSpecificRole Action into the main menu after cleanup results in duplicate items

//main.cpp
#include <QApplication>
#include <QMainWindow>
#include <QMenuBar>
#include <QAction>

class test: public QMainWindow
{
    Q_OBJECT;

public:
    test()
      :QMainWindow()
    {
        tt = new QMenu(this);
        mTest = new QAction(this) ;
        mAppSpec = new QAction(this) ;
        create();
    }

signals:
    void test1();

public slots:
    void create()
    {
//        delete mAppSpec;
        delete tt;

        QMenuBar *pMenuBar = menuBar();
        tt = new QMenu(this);
        tt->setTitle("Test");
        delete mTest;
        mTest = new QAction(this);
        mTest->setText("test2");
        connect (mTest, SIGNAL(triggered()),
                 this, SLOT(onClicked()));

        tt->addAction(mTest);

        delete mAppSpec;
        mAppSpec = new QAction(this);
        mAppSpec->setText("App Spec");
        mAppSpec->setMenuRole(QAction::ApplicationSpecificRole);
        connect (mAppSpec, SIGNAL(triggered()),
                 this, SLOT(onAppSpec()));

        tt->addAction(mAppSpec);

        pMenuBar->addMenu(tt);
    }
    void onClicked()
    {
        create();
    }

    void onAppSpec()
    {
        qDebug("app spec");
    }

private:
    QMenu *tt;
    QAction *mTest;
    QAction *mAppSpec;
};

int main(int argc, char *argv[])
{
    QApplication app (argc, argv);
    test *mw = new test;
    mw->show();
    return app.exec();
}

#include "main.moc"