fix bug where nil token was created when cancelling add card
fix bug where nil token was created when cancelling add card

stripe/stripe-ios,stripe/stripe-ios,stripe/stripe-ios,stripe/stripe-ios,stripe/stripe-ios,NewAmsterdamLabs/stripe-ios,stripe/stripe-ios,fbernardo/stripe-ios,NewAmsterdamLabs/stripe-ios,NewAmsterdamLabs/stripe-ios,fbernardo/stripe-ios,fbernardo/stripe-ios,fbernardo/stripe-ios,NewAmsterdamLabs/stripe-ios