NoMethodError in StoreController#add_to_cart


#1

Working through the Agile Web D. w/ Rails book on p114. I can
add single items of each to the cart but when I try to add a second item
I get the following error:

NoMethodError in StoreController#add_to_cart

You have a nil object when you didn’t expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.+

Any idea why this is happening? Thanks.

Frank.