Fix JTC crashing when shutdown while executing (#1960)

Author: MarqRazz

joint_trajectory_controller/include/joint_trajectory_controller/joint_trajectory_controller.hpp

@@ -183,8 +183,8 @@ class JointTrajectoryController : public controller_interface::ControllerInterfa
   using RealtimeGoalHandlePtr = std::shared_ptr<RealtimeGoalHandle>;
   using RealtimeGoalHandleBuffer = realtime_tools::RealtimeBuffer<RealtimeGoalHandlePtr>;
 
+  RealtimeGoalHandleBuffer rt_active_goal_;  ///< Currently active action goal, if any.
   rclcpp_action::Server<FollowJTrajAction>::SharedPtr action_server_;
-  RealtimeGoalHandleBuffer rt_active_goal_;       ///< Currently active action goal, if any.
   std::atomic<bool> rt_has_pending_goal_{false};  ///< Is there a pending action goal?
   rclcpp::TimerBase::SharedPtr goal_handle_timer_;
   rclcpp::Duration action_monitor_period_ = rclcpp::Duration(50ms);