item new created old not appear in my QTreeView

The problem is when i add item the old item was deleted why?
code:
Code:
void MainWindow::cambioRoster(QString barejid, QString resource)
{
    if(cliente.rosterManager().isRosterReceived() == true)
    {
        QXmppPresence::Type a = cliente.rosterManager().getPresence(barejid,resource).type();
        QIcon online;
        online.addFile(":/icons/user-online.png");
        if(ui->arbolConectados->findItems(barejid,Qt::MatchExactly).size() == 0)
        {
            QTreeWidgetItem *item = new QTreeWidgetItem();
            item->setText(0,barejid);
            ui->arbolConectados->addTopLevelItem(item);
        }
        if(a == QXmppPresence::Available)
        {
            QTreeWidgetItem *item = new QTreeWidgetItem();
            item->setText(0,resource);
            item->setIcon(0,online);
            ui->arbolConectados->findItems(barejid,Qt::MatchExactly)[0]->addChild(item);
        }
        if(a == QXmppPresence::Unavailable)
        {
            int i=0;
            while(i<ui->arbolConectados->findItems(barejid,Qt::MatchExactly)[0]->childCount() && ui->arbolConectados->findItems(barejid,Qt::MatchExactly)[0]->child(i)->text(0) != resource) //busqueda lineal
            {
                i++;
            }
            ui->arbolConectados->findItems(barejid,Qt::MatchExactly)[0]->takeChild(i);
            if(ui->arbolConectados->findItems(barejid,Qt::MatchExactly)[0]->childCount() == 0)
            {
                online.addFile(":/icons/user-offline.png");
            }
        }
        ui->arbolConectados->findItems(barejid,Qt::MatchExactly)[0]->setIcon(0,online);
    }
}