"TypeError: Cannot read property 'text' of null" with Tumbler.currentItem

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

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

    Component.onCompleted: {
        tumbler.currentIndex = 2
    }

    Row {
        Tumbler {
            id: tumbler
            model: 5
            // ...
        }

        Label {
            text: tumbler.currentItem.text
        }
    }
}

qrc:/main.qml:19: TypeError: Cannot read property 'text' of null