URGENT: critical error due to dynamic discounting

My has had a critical error when working on a product and I am unsure how to fix it, I have added a code to the class-manager file that fixes it for now but as soon as the theme will update it will cause the crash again.

The new code that fixed it:

if ( ! is_array( $conditions ) || empty( $conditions ) ) {
return false;
}

uasort( $conditions, array( $this, ‘sort_by_priority’ ) );

but when I try make this change in child theme I get error 2 in private