message: fix: check whether request is null
diff: @@ -79,6 +79,11 @@ int GeneralReaderOp::inference() {
  VLOG(2) << "(logid=" << log_id << ") var num: " << var_num
  << ") start to call load general model_conf op";
  + if (var_num < 1) {
  + LOG(ERROR) << "(logid=" << log_id << ") Failed get feed_var, var_num="
  + << var_num;
  + return -1;
  + }
  baidu::paddle_serving::predictor::Resource &resource =
  baidu::paddle_serving::predictor::Resource::instance();
  