Avoid passing Null to memcmp
Avoid passing Null to memcmp

As per discussion in - https://github.com/open-source-parsers/jsoncpp/issues/404
Null should not be pass to memcmp, it may show undesired behaviour, so avoid doing that using assertion.
Also, changed one direct "assert" to JSON_ASSERT - it will be decided if exceptions are used or not.
Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper