[TIMOB-13064] iOS: Date Picker getValue() returns null

var mainWindow = Ti.UI.createWindow({
    title : 'Lab',
    backgroundColor : 'white',
    fullscreen : false,
    navBarHidden : true,
    exitOnClose : true,
    orientationModes : [Titanium.UI.PORTRAIT]
});

var picker = Ti.UI.createPicker({
    type : Ti.UI.PICKER_TYPE_DATE,
    selectionIndicator : true,
    useSpinner : true
});

var showDate = Ti.UI.createButton({
    title : 'show date',
    bottom : 20
});
showDate.addEventListener('click', function(e) {
    alert(picker.getValue());
});

var view = Ti.UI.createView({
    width : Ti.UI.FILL,
    height : Ti.UI.FILL
});
view.add(picker);
view.add(showDate);

mainWindow.add(view);
mainWindow.open();