TOPIC: Error Invalid argument supplied for foreach appears on Confi

I am receiving this error twice on the confirmation page for every registration:
Warning: Invalid argument supplied for foreach() in /home/content/x/x/x/xxxxxxxxxx/html/administrator/components/com_dtregister/models/event.php on line 669

This error just started appearing on all Registration Confirmation Pages.

I've been using the latest version of DTRegister, and I have not made changes to joomla! config or DTRegister config.

Probably not a DTRegister issue directly, but something isn't playing nice with something else, and I don't have a clue as to what. I have done a search here, and looked into some of the issue reported with the same error.

At first, with some events, the registration did not appear on the back end in Records or the attendees list. I deleted and recreated events. I am still getting the error, but am receiving the registration email, the user is receiving the confirmation email, and the registrant is showing up on the Attendees list.