Always return result property on success

Author: ryanbrandenburg

src/JsonRpc/Serialization/Converters/ClientResponseConverter.cs

@@ -21,11 +21,14 @@ public override void WriteJson(JsonWriter writer, Response value, JsonSerializer
             writer.WriteValue("2.0");
             writer.WritePropertyName("id");
             writer.WriteValue(value.Id);
+            writer.WritePropertyName("result");
             if (value.Result != null)
             {
-                writer.WritePropertyName("result");
                 serializer.Serialize(writer, value.Result);
             }
+            else{
+                writer.WriteNull();
+            }
             writer.WriteEndObject();
         }
     }