[Bug] Customer changes payment method later

[migo315]

SyliusPayPalPlugin version affected: 1.6.0

Description
If the customer puts a few items in the shopping cart and wants to pay with e.g. ‘Cash on Delivery’ but then changes his mind and wants to pay with PayPal Express Checkout, this does not work. It runs into an error.

Steps to reproduce

• Add an item to your shopping cart
• Select payment method ‘Cash on Delivery
• Go to the last step ‘Checkout Complete’ but do not finalise the order
• Go back to the shopping basket or product detail page and click on Paypal Express Checkout.
• Now it runs into an error.