Fatal Error After Update

After the update to the latest version I got a Fatal Error when I check inside the order.
here the print out from the Fatal Error.
how can we fix this?

Uncaught Error: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class Korkmaz_woo_sales_contract_Admin does not have a method “vergi_no_dairesi”
in /home/mysite.com/tr.mysite.com/wp-includes/class-wp-hook.php on line 324

Call stack:

1. WP_Hook::apply_filters()
   wp-includes/class-wp-hook.php:348
2. WP_Hook::do_action()
   wp-includes/plugin.php:517
3. do_action()
   wp-content/plugins/woocommerce/includes/admin/meta-boxes/class-wc-meta-box-order-data.php:537
4. WC_Meta_Box_Order_Data::output()
   wp-admin/includes/template.php:1456
5. do_meta_boxes()
   wp-admin/edit-form-advanced.php:721
6. require('/home/mysite.com/tr...it-form-advanced.php')
   wp-admin/post.php:206