QML SpinBox: Customization example is broken

import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15

Window {
    width: 200
    height: 80
    visible: true

    SpinBox {
        id: control
        value: 50
        editable: true
        anchors.fill: parent

        contentItem: TextInput {
            z: 2
            text: control.textFromValue(control.value, control.locale)

            font: control.font
            color: "#21be2b"
            selectionColor: "#21be2b"
            selectedTextColor: "#ffffff"
            horizontalAlignment: Qt.AlignHCenter
            verticalAlignment: Qt.AlignVCenter

            readOnly: !control.editable
            validator: control.validator
            inputMethodHints: Qt.ImhFormattedNumbersOnly
        }

        up.indicator: Rectangle {
            x: control.mirrored ? 0 : parent.width - width
            height: parent.height
            implicitWidth: 40
            implicitHeight: 40
            color: control.up.pressed ? "#e4e4e4" : "#f6f6f6"
            border.color: enabled ? "#21be2b" : "#bdbebf"

            Text {
                text: "+"
                font.pixelSize: control.font.pixelSize * 2
                color: "#21be2b"
                anchors.fill: parent
                fontSizeMode: Text.Fit
                horizontalAlignment: Text.AlignHCenter
                verticalAlignment: Text.AlignVCenter
            }
        }

        down.indicator: Rectangle {
            x: control.mirrored ? parent.width - width : 0
            height: parent.height
            implicitWidth: 40
            implicitHeight: 40
            color: control.down.pressed ? "#e4e4e4" : "#f6f6f6"
            border.color: enabled ? "#21be2b" : "#bdbebf"

            Text {
                text: "-"
                font.pixelSize: control.font.pixelSize * 2
                color: "#21be2b"
                anchors.fill: parent
                fontSizeMode: Text.Fit
                horizontalAlignment: Text.AlignHCenter
                verticalAlignment: Text.AlignVCenter
            }
        }

        background: Rectangle {
            implicitWidth: 140
            border.color: "#bdbebf"
        }
    }
}

nativeIndicators: false
containmentMask: Item {
    height: contentItem.height
    width: contentItem.width - spinbox.up.indicator.width - spinbox.up.indicator.width
    anchors.centerIn: contentItem
}

property bool nativeIndicators: up.indicator.hasOwnProperty("_qt_default")
								&& down.indicator.hasOwnProperty("_qt_default")