wesboyt

Need to remove all undefined behavior logic to throw early

1

Replace with null values or refactor out.

[This test](https://github.com/amzn/ion-java/blame/d5939190808b815ec940ef5d45db0d39e9c3fb63/test/com/amazon/ion/SystemProcessingTestCase.java#L1024) assumes IVMs will be propagated by the user level writer APIs but without any actual userdata serialized we no longer roundtrip anything at all.