Null properties get converted to QVariant(void*) when put inside a QML model

I have a list of objects with properties, constructed by parsing a JSON string. Some of these properties are null. This list of object is then used as the model of a ListView component.

The problem is, any 'null' property is converted to a QVariant(void*) inside the list model, and there doesn't seem to be any way of knowing that this QVariant(void*) is a null value.

ListView
{
    Component.onCompleted:
    {
        var result = [{'test': null}];
        print("original value:", result[0].test);
        model = result;
        print("in model:", model[0].test);
    }

    delegate: Item
    {
        Component.onCompleted:
        {
            var t = modelData.test;
            print("in delegate:", t);
            print(t === null, t === undefined, t === false, t === "");
        }
    }
}

qml: original value: null
qml: in delegate: QVariant(void*)
qml: false false false false
qml: in model: QVariant(void*)

The real context: the JSON string is returned by a web service, and the null values are supposed to be strings. These strings are assigned to Text components. And because of this problem, I have no way of handling null strings correctly (without QML errors).