message: use only valid agents for rtree
diff: @@ -153,7 +153,7 @@ std::vector<ObservedWorld> World::Observe(
  void World::UpdateAgentRTree() {
  rtree_agents_.clear();
  - for (auto& agent : agents_) {
  + for (auto& agent : GetValidAgents()) {
  auto obj =
  agent.second->GetPolygonFromState(agent.second->GetCurrentState()).obj_;
  rtree_agent_model box;
  