Anonymous users cannot view their line item attributes.

Anonymous users never get access to view their previously chosen line item options. This is assuming the product is using a commerce_product_option option set.

Step to reproduce:

1. Add a new commerce product option set
2. Configure a product to use the option set.
3. Log out
4. Add the configured product line item to the cart
5. Edit the line item by navigating to the line item's display path and pass a query string of ?line_item_id=1234 (replacing 1234 with a valid line item id)

So the expected behavior is to see the default values of the line item edit form populated with the previously entered values. This works for admin and authenticated users. However, anonymous users simply see a blank form.

So, my first hunch was to look at permissions. Commerce line item module has an 'administer line items' permission that, when granted to anonymous, produced the desired behavior. However, it also gave anonymous access to edit any line item which was undesired.

I found a bug in commerce_product_attributes_access_to_line_item(), where sometimes the line item object passed to it is in fact sometimes simply a line item ID. I can't really figure out why that is happening, but I just threw in a condition to account for that happening, and this is working.

Feedback greatly appreciated, I know this module needs some love.