is not an array

Hi, first thank you for the modul, it works well, but there is the message I'm getting whern submitting new content:

* warning: usort() [function.usort]: The argument should be an array in /home/server/www/drupalbase/www/sites/vizy.cz/modules/taxonomy_hide/taxonomy_hide.module on line 110.

I'm not a programmer, so I don't now, may be its because there where no taxonomy term assigned, or maybe because its just not an array. Anyway, I think its a small leak.

Thank you.