Fatal Error: Unsupported Operand Types

I have this message at the bottom of some of my pages. Mainly in my Coursepress Pages while I am signed in.

" Fatal error: Unsupported operand types in /home/troyaust/public_html/wp-content/plugins/marketpress/includes/common/class-mp-cart.php on line 1319 "

I attached a screen shot if that may help.

What does this mean and is there anything I can do to fix it? Thank you!