code: protected T deserializeNullValue( JsonReader reader, JsonDeserializationContext ctx, JsonDeserializerParameters params ) {
          reader.skipValue();
          return null;
      }
docs: Deserialize the null value. This method allows children to override the default behaviour.
  
  @param reader {@link JsonReader} used to read the JSON input
  @param ctx Context for the full deserialization process
  @param params Parameters for this deserialization
  @return the deserialized object