Cron Error from pending relationships?

Thanks for the excellent module. I seem to be getting this whenever I run cron:

warning: Invalid argument supplied for foreach() in /var/www/thomas/lc3/sites/all/modules/user_relationships/plugins/user_relationship_node_access/user_relationship_node_access.module on line 144.

Which would be referring to this:

/**
 * List of pending relationships with between two users
 */
function _user_relationships_actions_between(&$viewer, &$viewed) {
  if ($viewer->uid == $viewed->uid) {
    return;
  }

Don't know what this means, sorry.