message: Fix RefChecker usage
  Summary:
  Fix stack-use-after-scope error
  Fix the `store_idx` for RefChecker.
diff: @@ -29,8 +29,9 @@ void set_up(ConfigFiles& conf) {
  s_is_initialized = true;
  }
  -std::unique_ptr<RefChecker> ref_checker_for_root_store(
  - const DexStoresVector& stores, ConfigFiles& conf, int min_sdk) {
  +std::unique_ptr<RefChecker> ref_checker_for_root_store(XStoreRefs* xstores,
  + ConfigFiles& conf,
  + int min_sdk) {
  auto min_sdk_api_file = conf.get_android_sdk_api_file(min_sdk);
  const api::AndroidSDK* min_sdk_api{nullptr};
  if (!min_sdk_api_file) {
  @@ -40,8 +41,9 @@ std::unique_ptr<RefChecker> ref_checker_for_root_store(
  } else {
  min_sdk_api = &conf.get_android_sdk_api(min_sdk);
  }
  - XStoreRefs xstores(stores);
  - return std::make_unique<RefChecker>(&xstores, /*store_idx*/ 0, min_sdk_api);
  + // The primary dex is the store 0, the secondary dexes are in store 1, and
  + // then other stores.
  + return std::make_unique<RefChecker>(xstores, /*store_idx*/ 1, min_sdk_api);
  }
  } // namespace
  @@ -63,7 +65,8 @@ void merge_model(Scope& scope,
  }
  TypeSystem type_system(scope);
  int32_t min_sdk = mgr.get_redex_options().min_sdk;
  - auto refchecker = ref_checker_for_root_store(stores, conf, min_sdk);
  + XStoreRefs xstores(stores);
  + auto refchecker = ref_checker_for_root_store(&xstores, conf, min_sdk);
  auto model =
  Model::build_model(scope, conf, stores, spec, type_system, *refchecker);
  model.update_redex_stats(mgr);
  