TWEAK: Update Null* type tests to test JSON unmarshalling.
TWEAK: Update Null* type tests to test JSON unmarshalling.

antony360/dbr,mailru/dbr,demdxx/dbr,mibk/ql,kevpie/dbr,playerbase/dbr,postfix/dbr,iyee/dbr,gocraft/dbr,joe-roth/dbr,orian/dbr