Assigning undefined to property results in vague error message

    Component {
        id: theComponent
        Item {
            property int horizontalAlignment
        }
    }
    function test_stuff() {
        var data = ({})
        data.horizontalAlignment = undefined
        var properties = { horizontalAlignment: data.horizontalAlignment }
        // QWARN  : [...]tst_textarea.qml: Could not set initial property horizontalAlignment
        var object = theComponent.createObject(parent, properties);
    }