Binding - null value

Item
{
    id: example

    property QtObject obj1
    property QtObject obj2: button.checked ? test: null

    QtObject { id: test }

    Column
    {
        Text { text: "obj1: " + obj1 }
        Text { text: "obj2: " + obj2 }

        Button
        {
            id: button
            text: "BUTTON"
            checkable: true
            checked: true
        }
    }

    Binding
    {
        target: example
        property: "obj1"
        value: obj2
    }
}