Error in log

Hi!!

First sorry for my poor english.

The plugin works fine to me, but if I enable debug I got the following error:

PHP Notice: Undefined index: ajax in /home/u733048850/public_html/wp-content/plugins/advanced-browser-check/advanced-browser-check.php on line 14

Is the plugin, the theme, the wordpress version?

WordPress 3.5
Graphene Theme.

https://sayaka.pusku.com

Thanks.

https://www.ads-software.com/extend/plugins/advanced-browser-check/