Error Messages as User

Hello,
I am registered on my Multisite as an admin, Piwik works perfectly. I am logged in as a normal user, I get error messages like this:

Warning: Invalid argument supplied for foreach () in /wp-content/plugins/wp-piwik/classes/WP_Piwik/Widget/SystemDetails.php on line 42

How do I fix this? I would like to thank you for the attention. (:

Best wishes