Fix for 404 when a user removes an item from the cart with the X button

With the spree_promo gem installed I received a 404 page whenever I had a single LineItem in my cart and pressed the X button on the right side of that LineItem on the cart page.

Inspecting more closely the 404 occurred after a database attempt to find the LineItem with the ID I had removed earlier in that same request. I solved the issue by reloading the Order object before the existing code iterates through the LineItems.

This issue may also exist in spree_core, so you might want to check this too.