[REG 5.9.3 => 5.9.4] Popup opened at 0, 0 has no background

import QtQuick 2.9
import QtQuick.Controls 2.2

ApplicationWindow {
    visible: true
    width: 640
    height: 480

    Button {
        text: "Open"
        onClicked: popup.open()
    }

    Popup {
        id: popup
        width: 200
        height: 200
        modal: true

        Rectangle {
            anchors.fill: parent
            color: "transparent"
            border.color: "darkorange"
        }
    }
}