Fix planning_scene_monitor sync when passed empty robot state

moveit_ros/planning/planning_scene_monitor/src/planning_scene_monitor.cpp

@@ -731,6 +731,10 @@ bool PlanningSceneMonitor::newPlanningSceneMessage(const moveit_msgs::msg::Plann
 
     if (!scene.is_diff && parent_scene_)
     {
+      // if the scene does not contain a robot state then use the latest value from the current_state_monitor_
+      // so that we are not updating the scene with stale values for the robots state.
+      if (scene.robot_state.joint_state.name.empty())
+        parent_scene_->setCurrentState(*current_state_monitor_->getCurrentState());
       // clear maintained (diff) scene_ and set the full new scene in parent_scene_ instead
       scene_->clearDiffs();
       result = parent_scene_->setPlanningSceneMsg(scene);