Possible to empty completed orders

What steps will reproduce the problem?
1. Place an order successfully
2. Make any call in the code to order.empty!

This can happen through a few edge cases and selected actions in the store.

On the admin side, this winds up showing completed orders with no items - only 
a shipping cost. Puzzling to say the least.

What is the expected output? What do you see instead?

Completed orders should never have their items modified.

Original issue reported on code.google.com by subim...@gmail.com on 14 Sep 2010 at 6:38

rdp / substruct

Possible to empty completed orders #220