jsonrpc.DefaultErrorEncoder does not meet JSON RPC v2.0 specification

From response specification (https://www.jsonrpc.org/specification):

Id
This member is REQUIRED.
It MUST be the same as the value of the id member in the Request Object.
If there was an error in detecting the id in the Request object (e.g. Parse error/Invalid Request), it MUST be Null.

Currently, DefaultErrorEncoder is set to nil:

	_ = json.NewEncoder(w).Encode(Response{
		JSONRPC: Version,
		Error:   &e,
	})