Make sure not to validate/submit the customer profiles when unnecessary

Problem/Motivation

I need to hide the shipping information checkout pane on my project when purchasing non physical products.
When doing that in a form_alter hook, you also need to wipe the profile that has been previously stored in the form state array by the checkout pane callback.
Currently, this will lead to an error because the checkout pane validate/submit callbacks will try to save the profile, without checking if it's still there.

Proposed resolution

Skip validation/submit when the profile can't be found in the $form_state array.

Remaining tasks

TBD.

User interface changes

None.

API changes

None.

Data model changes

None.