CLONE -QTreeWidget - after removing/adding back children of a child, the chidren indicator ('+') of this child gets lost

#include <QApplication>
#include <QtGui>

class CMyView : public QWidget
{
	Q_OBJECT
public:
	CMyView()
	{	
		treeWidget = new QTreeWidget;
		pushButton = new QPushButton(tr("click me"));

		m_pItem = new QTreeWidgetItem(); 
		m_pItem->setText(0, "parent"); 
		treeWidget->addTopLevelItem(m_pItem); 
		m_pItem->setExpanded(true);


		m_pItemChild = new QTreeWidgetItem(); 
		m_pItemChild->setText(0, "child_1"); 
		m_pItem->addChild(m_pItemChild); 

		QTreeWidgetItem* pItem = new QTreeWidgetItem(); 
		pItem->setText(0, "child_2"); 
		m_pItemChild->addChild(pItem); 

		pItem = new QTreeWidgetItem(); 
		pItem->setText(0, "child_3"); 
		m_pItemChild->addChild(pItem); 
	 

		QHBoxLayout *hL = new QHBoxLayout;
		hL->addStretch();
		hL->addWidget(pushButton);

		QVBoxLayout *vL = new QVBoxLayout;
		vL->addWidget(treeWidget);
		vL->addLayout(hL);

		setLayout(vL);

		connect(pushButton, SIGNAL(clicked()), this, SLOT(on_clicked())); 
	}

public slots:
	void on_clicked()
	{
		for (qint32 i = 0; i < m_pItemChild->childCount(); i++) 
		{ 
			m_pItem->removeChild(m_pItemChild); 
			m_pItem->addChild(m_pItemChild); 

			QTreeWidgetItem* pChild = m_pItemChild->takeChild(i);
			if (pChild) 
			{
			m_pItemChild->insertChild(i, pChild);
			}
		}
	}

private:
     QTreeWidgetItem *m_pItem;
     QTreeWidgetItem *m_pItemChild;
     QTreeWidget *treeWidget;
     QPushButton *pushButton;
};

#include "main.moc"


int main(int argc, char *argv[])
{
     QApplication app(argc, argv);

     CMyView *mv = new CMyView;
     mv->show();

     return app.exec();
}

void on_clicked()
{
       setUpdatesEnabled(false);
       .......
       setUpdatesEnabled(true);
}