message: fix primitive gap keeping
diff: @@ -139,6 +139,7 @@ class PrimitiveGapKeeping : public Primitive,
  }
  Trajectory Plan(float delta_time, const ObservedWorld& observed_world) {
  auto traj = BehaviorIDMLaneTracking::Plan(delta_time, observed_world);
  + return traj;
  }
  };
  