[Fix]fix err when exporting model meta for sparse estimator (#219)
[Fix]fix err when exporting model meta for sparse estimator (#219)

Co-authored-by: wuliangchao <5a3da298ddd80d4207c61bab5a9ab735b3345c91@bytedance.com>
bytedance/fedlearner,bytedance/fedlearner,bytedance/fedlearner,bytedance/fedlearner,bytedance/fedlearner,bytedance/fedlearner,bytedance/fedlearner