if (collection == null) {
collection = new ArrayList();
propDesc.getWriteMethod().invoke(policy, collection);
}
component = new AjaxPalettePanel("field", new PropertyModel(policy, field.getName()),
new ListModel<String>(values));
item.add(component);
item.add(getActivationControl(component,
!collection.isEmpty(), new ArrayList<String>(), new ArrayList<String>()));