HS + Views: exposed filters in page + hs_taxonomy_views results in user warning: SELECT COUNT(*) FROM () count_alias

I see a related warning when setting "Display the node count" or "Require associated node" in Views Hierarchical Select settings for an exposed filter is set.

I've been debugging and in line

520 $count_query = $temp_view->build_info['count_query']; 

after executing $temp_view->build($display_id);

$count_query is empty so all str_replace after to calculate node counts are not working.

I've some filters in the view, node type, taxonomy voc., etc...

I don't know what is causing build_info['count_query'] being completly empty always.