2
Haven't seen this myself, but found the following which sound as though they maybe relevant by doing a search on comment_view.php and Undefined index: com_order
https://xoops.org/modules/newbb/viewtopic.php?topic_id=14821&forum=21#forumpost60921
https://xoops.org/modules/newbb/viewtopic.php?topic_id=14502&forum=3#forumpost59198
https://xoops.org/modules/newbb/viewtopic.php?topic_id=15057&forum=4#forumpost62256