Support Closing Address Validation with the close button

Problem/Motivation

If the address validation confirmation dialog is opened, and the close (x) dialog button is invoked, you will not be able to continue checkout.

This is because the isValidating property is not reset when this button is invoked, unlike when the "Let me change the address" button is invoked.

Steps to reproduce

Enter an invalid address.
Submit the form.
Invoke the Close(X) button.
Submit the form...nothing happens.