If you make a new order status it adds an entry to the db similar to:

+----+-----------+----------+-----------+
| id | is_active | name     | status_id |
+----+-----------+----------+-----------+
|  7 |         1 | REJECTED |      1003 | 
+----+-----------+----------+-----------+

On line 1300 of kernel/classes/ezorder.php you get eZOrder::statusName using the $this->StatusID which in the above case is 7 rather than 1003. Because of this, the eZOrderStatus::fetchByStatus fails as it cannot find a DB entry with a status_id of 7. It works if you change the call to eZOrderStatus::fetch. Or eZOrder could be changed to stored the status_id number rather than id.

Steps to reproduce

Log into the admin interface and go to Webshop. Click Order status in the left menu. Add a new order status.

Create an order that uses this status.

Try to view the order list. You should get:
Fatal error: Call to a member function attribute() on a non-object in /var/www/html/designtest/kernel/classes/ezorder.php on line 1302