Fixed error showing on Stripe Checkout (#15719)
Fixed error showing on Stripe Checkout (#15719)


`window.location.assign` does not return anything, so `result.error` was
failing because `result` was undefined. We've moved the handling of the
result of `redirectToCheckout` to be specific to that promise. We've
also removed the use of `catch` because all it did was rethrow the
error, which is default behaviour.
TryGhost/Ghost,TryGhost/Ghost,TryGhost/Ghost