handle price sets with one option being $0
handle price sets with one option being $0

When you select a priceset with the value 0, the form properly hides
the credit card input fields.

However, we still try to submit a credit card to stripe which results in
an error.

mattwire/com.drastikbydesign.stripe,mattwire/com.drastikbydesign.stripe,mattwire/com.drastikbydesign.stripe