Reject nil keys

[jshawl]

When listing charges, if a user specifies a customer_id, but
customer_id is nil, raise a TypeError instead of silently omitting
the key and returning charges for any user.

[brandur-stripe]

Thanks for the PR!

I'm generally in favor of this sort of safety check, but unfortunately it's a breaking change — it's a fairly common pattern in Ruby (for better or for worse) to pass that was received via something like a form into a set of parameters like these ones, and it's likely that someone out there is relying on the fact that a nil customer_id will fall back to general behavior.

In the spirit of #637, I'm going to mark this with the "future" tag for now as an improvement that we could introduce the next time we do a major version bump.

[ob-stripe]

Hey @jshawl, sorry for the very late reply. We're currently preparing a new major release (#815) and have been debating whether to include your change or not. We've decided not to, as we think this change would be unnecessary painful for many existing users. It's something that would have been nice to have from the start but is hard to add at this point in time.

Thanks again for the contribution and for your understanding!