Isn't null an object?
per the RFC,
"JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays)."
"An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array."
2.1. Values
A JSON value MUST be an object, array, number, or string, or one of
the following three literal names:
false null true
... so what you're receiving is technically a valid JSON value according to the RFC, no?(I am so sorry for being this pedantic - but that RFC is marked 'informational', it's not actually a standard so much as a suggestion, and even worse, RFC 7159 obsoletes it and is an IETF standards track document - check out http://tools.ietf.org/html/rfc7159. The ambiguity is definitely removed in the updated version.)
vs
null
I'm pretty sure they're both valid.