Do not throw an exception if an invalid item is detected in selectivity.js

Selectivity.processItem = function(item) {
    if (Selectivity.isValidId(item)) {
        return { id: item, text: '' + item };
    } else if (item && (Selectivity.isValidId(item.id) || item.children) && isString(item.text)) {
        if (item.children) {
            item.children = Selectivity.processItems(item.children);
        }        return item;
    } else {
        throw new Error('invalid item');
    }
};