PHP error

I got this PHP error:

Warning: Undefined array key “cols” in /customers/7/5/e/****/httpd.www/cultuur/wp-content/plugins/press-permit-core/classes/PublishPress/Permissions/DB/Groups.php on line 424 Warning: Cannot modify header information – headers already sent by (output started at /customers/7/5/e/lucasgent.be/httpd.www/cultuur/wp-content/plugins/press-permit-core/classes/PublishPress/Permissions/DB/Groups.php:424) in /customers/7/5/e/****/httpd.www/cultuur/wp-admin/includes/misc.php on line 1431

Warning: Cannot modify header information – headers already sent by (output started at /customers/7/5/e/****/httpd.www/cultuur/wp-content/plugins/press-permit-core/classes/PublishPress/Permissions/DB/Groups.php:424) in /customers/7/5/e/*****/httpd.www/cultuur/wp-includes/functions.php on line 7049

Warning: Cannot modify header information – headers already sent by (output started at /customers/7/5/e/****/httpd.www/cultuur/wp-content/plugins/press-permit-core/classes/PublishPress/Permissions/DB/Groups.php:424) in /customers/7/5/e/****/httpd.www/cultuur/wp-admin/admin-header.php on line 9

I went to groups.php and changed line 424 from:

if ('all' != $args['cols']) {

to:

if (isset($args['cols']) && 'all' != $args['cols']) {

and everything started working again. That error in my dashboard isn’t present anymore.