MarketPress - error in marketpress.php after checkout

I get this error message in Marketpress after the checkout is complete...
Warning: Invalid argument supplied for foreach() in /home/synergy7/public_html/ on line 2064

After much testing:
Logged in user, Not logged in user, coupon code, no coupon code, 1 item in order, multiple items in order.

I have determined that it's only when a coupon code is used, doesn't seem to matter about the other factors mentioned or any specific combination of those. Just using a coupon code seems to be the problem.

It will complete the order and seems to work fine, but that error appears on the Thank You page and in the header as well and will not go away from the header when clicking on other pages of the site. It will only go away when you manually go and remove the cookies, then refresh.

I'm using WP Multisite, with BuddyPress, Gridmarket theme. All the latest releases.