message: Fix error getting permission_object from db
diff: @@ -724,7 +724,7 @@ void chain_controller::update_global_properties(const signed_block& b) {
  active_producers_authority.accounts.push_back({{name, config::ActiveName}, 1});
  }
  - auto po = _db.get<permission_object, by_owner>( boost::make_tuple(config::ProducersAccountName, config::ActiveName) );
  + auto& po = _db.get<permission_object, by_owner>( boost::make_tuple(config::ProducersAccountName, config::ActiveName) );
  _db.modify(po,[active_producers_authority] (permission_object& po) {
  po.auth = active_producers_authority;
  });
  