自定义错误message信息为null也序列化

而且 目前有一个问题是 使用 自定义错误码 返回 必须携带message 即使 message写了 null message 变成了null，能否对message支持空逻辑？

Start by reproducing the custom error-code response described in the issue and trace where the null message is serialized. Determine the intended empty-message behavior, then verify the response and add or update tests covering a null message.

Written by the indexing model from the issue text.