Plugins which wrap the selectmenu content make it non-clickable

e.g. when using the jScrollPane plugin for a custom scrollbar inside the menu dropdown like this:

```js
$('select').selectmenu().next('span').find('a.ui-selectmenu').one('click', function() {
	$('ul.ui-selectmenu-menu-dropdown:visible').jScrollPane({
		isScrollableH: false
	});
});
```