message: Make `null` a valid result value.
diff: @@ -114,7 +114,7 @@ export interface ResponseMessage extends Message {
  * The result of a request. This member is REQUIRED on success.
  * This member MUST NOT exist if there was an error invoking the method.
  */
  - result?: string | number | boolean | object;
  + result?: string | number | boolean | object | null;
  /**
  * The error object in case a request fails.
  