Make parent taxonomies unselectable not working

So far only your plugin seems to have this useful option, but sadly is not working well:

when inside the categories metabox the “Most used” tab is checked, the parent category is still selectable (even if it doesn’t work AFTER i hit update). And when “All categories” tab is selected it does it well hiding the parent category button, BUT then it treats other parentless categories as parents and disables them also (which shouldn’t).

it’d be very helpful to have this feature working well to prevent users from selecting the wrong (parent) category when it’s needed to limit the post category only to one.

Thank you very much.