Sort on Description error

I'm not sure whether the option to sort on description was intentional, but on doing so the following error message appears:

* warning: usort() [function.usort]: Invalid comparison function in /home/xxxxxxx/public_html/sites/all/modules/filebrowser/filebrowser.module on line 594.
* warning: usort() [function.usort]: Invalid comparison function in /home/xxxxxxx/public_html/sites/all/modules/filebrowser/filebrowser.module on line 595.

Hope it helps,

Paul