Searching for a group that doesn't match an existing group gives a warning in the logs

If i navigate to this url http://example.com/civicrm/group?reset=1, and enter some characters that don't match an existing group name, one gets the expected results ' No matching groups .......'. but checking the recent log messages here http://example.org/admin/reports/dblog (Drupal), you get a warning message: Invalid argument supplied for foreach() in CRM_Utils_JSON::encodeDataTableSelector() (line 122 of ../sites/all/modules/civicrm/CRM/Utils/JSON.php). See attached file for more details when debugging is enabled