Iceberg: HIVE_METASTORE_WAREHOUSE_EXTERNAL is ignored when initializing HiveCatalog

(executor-thread-1) Unhandled exception returning INTERNAL_SERVER_ERROR : java.lang.NullPointerException: Warehouse location is not set: hive.metastore.warehouse.external.dir=null

  private String getExternalWarehouseLocation() {
    String warehouseLocation = conf.get(HiveConf.ConfVars.HIVE_METASTORE_WAREHOUSE_EXTERNAL.varname);
    Preconditions.checkNotNull(warehouseLocation,
        "Warehouse location is not set: hive.metastore.warehouse.external.dir=null");
    return warehouseLocation;
  }

 public void initialize(String inputName, Map<String, String> properties) {
    this.catalogProperties = ImmutableMap.copyOf(properties);
....
    if (properties.containsKey(CatalogProperties.WAREHOUSE_LOCATION)) {
      this.conf.set(HiveConf.ConfVars.METASTORE_WAREHOUSE.varname,
          LocationUtil.stripTrailingSlash(properties.get(CatalogProperties.WAREHOUSE_LOCATION)));
    }
}