Combobox indicator in a pop-up is lost if pop-up closed and re-opened

import QtQuick 2.0
import QtQuick.Window 2.0

Window {
    id: window
    width: 400
    height: 400
    visible: true
    title: "QTBUG-61334"

    Canvas {
        id: canvas
        width: 12
        height: 8
        contextType: "2d"
        onAvailableChanged: print("available", available)
        onContextChanged: print("context", context)

        Timer {
            running: true
            interval: 1000
            repeat: true
            onTriggered: {
                canvas.parent = canvas.parent ? null : window.contentItem
            }
        }

        onPaint: {
            context.reset();
            context.moveTo(0, 0);
            context.lineTo(width, 0);
            context.lineTo(width / 2, height);
            context.closePath();
            context.fillStyle = "#21be2b";
            context.fill();
        }
    }
}