Preconditions:

Added virtual product

Steps to reproduce

1. Go to storefront {host}/product-catalog
2. Add virtual product to cart.
3. Go through checkout process.
4. Being on checkout step 'Payment' click on 'Go back' button.

Actual result:

An error 400 bad request occurred while user click on 'Go back' button on payment view.

Argument '$step' has a bad state: Unable to execute checkout step: summary 

Expected result:

User can go back to previous view without any errors.