Set primary account address as the default

The shipping select no longer defaults to the primary account as
orderFulfillment.getShippingAddress() is no longer null with recent
changes. This checks to see if the addressID returned is an empty string
and if so, sets the accountAddressID to be the account primary
addressID.
You are right, that if I enter a new address that is missing required fields it returns me to the select with the primary account selected.