Assert on startup with Controls2 ToolTip

import QtQuick 2.7
import QtQuick.Controls 1.4
import QtQuick.Controls 2.0 as Controls
import QtQuick.Layouts 1.0

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Item {

        anchors.fill: parent

        Rectangle {

            MouseArea {
                id: ma
                anchors.fill: parent
                hoverEnabled: true
            }

            anchors.centerIn: parent
            width: 100
            height: 100
            color: "red"
            Controls.ToolTip.text: "aa"
            Controls.ToolTip.visible: ma.containsMouse

        }

    }
}