error on coursepress unit page

and this problems :
Warning: Creating default object from empty value in /home/fumahtay/public_html/wp-content/plugins/coursepress/includes/classes/class.shortcodes.php on line 3091

Warning: array_key_exists(): The first argument should be either a string or an integer in /home/fumahtay/public_html/wp-includes/cache.php on line 672

Warning: array_key_exists(): The first argument should be either a string or an integer in /home/fumahtay/public_html/wp-includes/cache.php on line 672

Warning: array_key_exists(): The first argument should be either a string or an integer in /home/fumahtay/public_html/wp-includes/cache.php on line 672

in this page :
http://www.itstar.ir/courses/aenean-auctor-nec-magna-sed-mattis/units/sed-egestas-erat-nec-purus/