Throw runtime exception is value is used from an uninitialized value-object

[SteveDunn]

It's impossible to guarantee that all value-objects will be initialized, for instance, new CustomerId[10].

We can pick up a lot of situations where an attempt is made to default a value-object, but for those where we can't, we need a flag in the type that is checked at runtime and throws an exception if the value-object's value is used.