Can't remove all community tags from node.

I use the community tags module as an API. It's working well, but if I want to remove all tags from a node the changes aren't saved, because processed_terms is empty and the loop in md_postfach_tag_node_form_submit()

foreach ($processed_terms as $vid => $processed_terms_for_vocabulary) {...}

never will be entered. I guess if All terms from just one vocabulary should get removed it won't work too.