Change behaviour of Spree::Address.build_default
Change behaviour of Spree::Address.build_default

Instead of the first country found, please raise an error if
the default country ISO code does not have an associated country.

The issue referenced in the spec, https://github.com/spree/spree/issues/1142,
is people complaining about no states found for Nil, which only ever
happened because Spree::Country.default would silently fail before.

Arpsara/solidus,pervino/solidus,jordan-brough/solidus,Arpsara/solidus,Arpsara/solidus,pervino/solidus,Arpsara/solidus,pervino/solidus,pervino/solidus,jordan-brough/solidus,jordan-brough/solidus,jordan-brough/solidus