Invalid argument warning on search page

My search page has started to display this warning:

Warning: Invalid argument supplied for foreach() in /home/magantne/public_html/wp-content/plugins/membership/membershipincludes/classes/membershippublic.php on line 2057

Warning: Invalid argument supplied for foreach() in /home/mysite/public_html/wp-content/plugins/membership/membershipincludes/classes/membershippublic.php on line 2057

It appears on my search page. Any ideas how I can fix please?