Incorrect deserialization of NULL value

Gson instance inside org.opendaylight.jsonrpc.bus.jsonrpc.JsonRpcBaseMessage is created with default options which include serializeNull = false.

As a consequence, if JsonObject has property with null value, it is incorrectly deserialized as empty object.

eg:

{"accept":

{"array-element":null}

}}

is being serialized as

{"accept":{"array-element":{}}}}

Problem escalate if https://jira.opendaylight.org/browse/YANGTOOLS-1003 is involved in serialization pipeline:

{"accept":

{"array-element":null}

}}

should become

{"accept":[null]}

but is

{"accept":{}}