Debug Error in Wp-Admin

When I turn on the debug and I go to the All Users Page in the Admin Area, is see in the header this error:
Notice: Undefined offset: 0 in /var/www/vhosts/xxxxxx/xxxxxxxx.com/content/plugins/wordpress-social-login/includes/services/wsl.user.data.php on line 218 Notice: Trying to get property of non-object in /var/www/vhosts/xxxxxxxx/xxxxxx.com/content/plugins/wordpress-social-login/includes/services/wsl.user.data.php on line 218

And it is repeated at least 3-4 times depends on how many users are regirested on the web site.

Can you tell how can I fix this stuff? I would like to have a clean website without any PHP errors

thank you!

http://wordpress.org/extend/plugins/wordpress-social-login/