JSON.toJSON(Object object, JSONWriter.Feature... features)转JSONObject的时候，如果对象里面有List, 内部递归JSON.toJSON的时候features不会传递

比如： JSONObject newData = (JSONObject)JSON.toJSON(data,Feature.WriteNulls);
当data对象中有List的时候，List中的空值依旧不会写入到JSONObject 中，从源码中看是因为ObjectWriterAdapter.toJSONObject(T object, long features)方法中在递归调用JSON.toJSON(item)的时候，没有传递Feature.WriteNulls

Start in ObjectWriterAdapter.toJSONObject(T object, long features), then trace its recursive JSON.toJSON(item) call for objects containing a List. Done means Feature.WriteNulls is preserved during nested conversion so null values inside the List appear in the resulting JSONObject.

Written by the indexing model from the issue text.