Ancestor's activeFocus bound to a grouped property gives strange errors upon destruction

import QtQuick 2.6
import QtQuick.Window 2.2

Window {
    id: window
    width: 360
    height: 360
    visible: true

    Component {
        id: emptyItem
        Item { }
    }

    Component {
        id: testItem
        Item {
            id: myItem
            Item {
                layer.enabled: myItem.activeFocus // <== any grouped property bound to ancestor's activeFocus
            }
        }
    }

    Component.onCompleted: {
        // 2 levels of parents, intentionally, to make sure that the potential fix
        // does not rely on something in the immediate parent. the problematic focus
        // clearing can originate from one of the grand parents. in this example, the
        // warning is thrown during the destruction of _grandparent_.

        var grandparent = emptyItem.createObject(window.contentItem, {objectName: "grandparent"})
        var parent = emptyItem.createObject(grandparent, {objectName: "parent"})
        var child = testItem.createObject(parent, {objectName: "child"})
        child.forceActiveFocus()
        grandparent.destroy(0)
    }
}