hide_empty="true" not working in the filter?

Hi,

On this page you can see all national park taxonomies are showing as filter options: http://nationalparktraveller(dot)com/hotels/
p.s. replace (dot) with a . to make the link work

If I understand the hide_empty="true" setting correctly … the list of taxonomies should only be showing those that have posts attached, i.e. the empty one's are hidden.

Is that what hide_empty="true" means and does?

Here is the filter code I have used with the hide_empty="true" setting in the code.

	[wpml-string context="wpv-views"]Search by National Parks:[/wpml-string] 
	[wpv-control taxonomy="destination-by-national-park" url_param="national-park" type="checkboxes" hide_empty="true"]
	[wpv-filter-submit name="Search"]

Have I done something wrong?

Thanks
Nick