Fatal error: Uncaught Error: Call to a member function get() on null in /var/sites/m/mm/public_html/system/library/weight.php:9 Stack trace: #0

Question

I m getting error in open cart Fatal error: Uncaught Error: Call to a member function get() on null in /var/sites/m/mm/public_html/system/library/weight.php:9 Stack trace: #