message: ACC model fixed when no leading vehicle present
diff: @@ -314,14 +314,13 @@ std::pair<double, double> BaseIDM::GetTotalAcc(
  double vel_i = ego_vehicle_state(StateDefinition::VEL_POSITION);
  bool interaction_term_active = rel_values.has_leading_object;
  - if (param_coolness_factor_ > 0.0f) {
  + if (interaction_term_active) {
  + if (param_coolness_factor_ > 0.0) {
  acc = CalcACCAcc(rel_distance, vel_i, vel_front, rel_values.ego_acc,
  rel_values.leading_acc);
  - traveled_ego = 0.5f * acc * dt * dt + vel_i * dt;
  - traveled_other = vel_front * dt;
  - rel_distance += traveled_other - traveled_ego;
  - } else if (interaction_term_active) {
  + } else {
  acc = CalcIDMAcc(rel_distance, vel_i, vel_front);
  + }
  traveled_ego = 0.5f * acc * dt * dt + vel_i * dt;
  traveled_other = vel_front * dt;
  rel_distance += traveled_other - traveled_ego;
  