"unexpected end of JSON input" when result is null

[nzdjb]

I'm making calls to an API that returns null for some calls (https://metaname.net/api/1.1/doc). When I successfully make these calls, I receive an error of "unexpected end of JSON input".

Example debug output:

--> {"jsonrpc":"2.0","method":"configure_zone","params":["xxxx","xxxxxxxxxxxxxxxxxxxxxxx","testzone.nz",[],null],"id":2283}
<-- {"result":null,"jsonrpc":"2.0","id":2283}

The spec doesn't explicitly say whether null is an allowed result value, but the implication seems to be that any value is valid. So a successful response with a result of null should not produce an error and should write nil to the request result.