ERROR

Hi, I installed this plugin in free version and I must say that it is perfect. But sometimes it transmits this error in the most voted section (on my site it is on the footer) Can you tell me how I can solve it?

NOTICE: UNDEFINED INDEX: CAT IN /HOME/JH13866B/PUBLIC_HTML/WP-CONTENT/PLUGINS/WP-REVIEW/INCLUDES/FUNCTIONS.PHP ON LINE 2818

The page I need help with: [log in to see the link]