Warnings when creating embedded Menus with Instantiator

[ribtoks]

I'd like to create a Menu in QML application that has other Menus depending on some Model. When I use Instantiator for that, items which are being created are parented to the Instantiator itself and when adding them to top-level Menu, it complains about __parentMenu being null

Menu {
    title: qsTr("Top-Level Menu")
    id: topMenu

    Instantiator {
        model: aTopLevelModel
        onObjectAdded: topMenu.insertItem( index, object )
        onObjectRemoved: topMenu.removeItem( object )

        delegate: Menu {
            id: innerMenu
            title: qsTr("Inner Menu")

            Instantiator {
                model: aTopLevelModel.getInnerModel(index)
                onObjectAdded: innerMenu.insertItem( index, object )
                onObjectRemoved: innerMenu.removeItem( object )

                delegate: MenuItem {
                    text: qsTr("Menu action!")
                    onTriggered: {
                        console.log("Action of inner menu")
                    }
                }
            }
        }
    }
}

The warning I'm observing is: Menu.qml:149: TypeError: Cannot read property '__contentItem' of null

Where the line 149 is property var __parentContentItem: __parentMenu.__contentItem.

How can I overcome this Warning being produced?

Qt version is 5.5.1. This behavior is observed undre OS X and Windows versions of Qt.