When attempting to update an order and notify the customer after clicking on add order history (in admin--Orders-->status & Comments) I get the following only for guests. When clicking back from the below error message the status and message is saved to the database but the email is not sent. If a person creates a customer account the update works as expected and sends the email.
There has been a critical error processing your request
Error: Could not load model checkout/fast_checkout
Trace:
#0/devshop/shop/core/helper/utils.php:1608
#1 /devshop/shop/admin/model/sale/order.php:1143
#2 /devshop/shop/admin/controller/pages/sale/order.php:1156
#3 devshop/shop/core/engine/dispatcher.php:306
#4 //devshop/shop/core/engine/dispatcher.php:341
#5/devshop/shop/core/engine/page.php:110
#6 /devshop/shop/core/engine/router.php:204
#7 /devshop/shop/core/engine/router.php:86
#8 /devshop/shop/index.php:97
in /devshop/shop/core/engine/loader.php on line 126
