get_table_rsgroup ignored the existence of rsgroup config for namespace

public GetRSGroupInfoOfTableResponse getRSGroupInfoOfTable(RpcController controller,
  GetRSGroupInfoOfTableRequest request) throws ServiceException {
  TableName tableName = ProtobufUtil.toTableName(request.getTableName());
  ...
  try {
    ...
    GetRSGroupInfoOfTableResponse resp;
    TableDescriptor td = master.getTableDescriptors().get(tableName);
    if (td == null) {
      resp = GetRSGroupInfoOfTableResponse.getDefaultInstance();
    } else {
      RSGroupInfo rsGroupInfo = null;
      if (td.getRegionServerGroup().isPresent()) {
        rsGroupInfo = master.getRSGroupInfoManager().getRSGroup(td.getRegionServerGroup().get());
      }
      if (rsGroupInfo == null) {
        rsGroupInfo = master.getRSGroupInfoManager().getRSGroup(RSGroupInfo.DEFAULT_GROUP);
      }
      resp = GetRSGroupInfoOfTableResponse.newBuilder()
        .setRSGroupInfo(ProtobufUtil.toProtoGroupInfo(rsGroupInfo)).build();
    }
    ...
    return resp;
  } catch (IOException e) {
    throw new ServiceException(e);
  }
}