mapToGlobal can crash

QQuickItem *myItem = new QQuickItem;
myItem->mapToGlobal(QPointF(0,0));

import QtQuick 2.0

Item {
    width: 400
    height: 400

    Component {
        id: rectComponent
        Rectangle {}
    }

    Component.onCompleted:  {
        var obj = rectComponent.createObject(null);
        obj.mapToGlobal(0,0)
    }
}