set position values to nan when sending velocity setpoint

src/px4_connection/src/px4_controller.cpp

@@ -274,6 +274,10 @@ private:
         msg.velocity[0] = velocity[0];
         msg.velocity[1] = velocity[1];
         msg.velocity[2] = D_SPEED(velocity[2]);
+        for (int i = 0; i < 3; i++)
+        {
+            msg.position[i] = NAN;
+        }
 
         publish_trajectory_setpoint(msg);
     }