navigator mission_result fix increment sign

src/modules/navigator/navigator.h

@@ -233,7 +233,7 @@ public:
 
 	orb_advert_t	*get_mavlink_log_pub() { return &_mavlink_log_pub; }
 
-	void		increment_mission_instance_count() { _mission_instance_count++; }
+	void		increment_mission_instance_count() { _mission_result.instance_count++; }
 
 	void 		set_mission_failure(const char *reason);
 
@@ -290,8 +290,6 @@ private:
 	position_setpoint_triplet_s			_takeoff_triplet{};	/**< triplet for non-mission direct takeoff command */
 	vehicle_roi_s					_vroi{};		/**< vehicle ROI */
 
-	int		_mission_instance_count{-1};	/**< instance count for the current mission */
-
 	perf_counter_t	_loop_perf;			/**< loop performance counter */
 
 	Geofence	_geofence;			/**< class that handles the geofence */

src/modules/navigator/navigator_main.cpp

@@ -497,7 +497,7 @@ Navigator::task_main()
 				publish_vehicle_command_ack(cmd, vehicle_command_s::VEHICLE_CMD_RESULT_ACCEPTED);
 
 			} else if (cmd.command == vehicle_command_s::VEHICLE_CMD_MISSION_START) {
-				if (get_mission_result()->valid &&
+				if (_mission_result.valid &&
 				    PX4_ISFINITE(cmd.param1) && (cmd.param1 >= 0) && (cmd.param1 < _mission_result.seq_total)) {
 
 					_mission.set_current_offboard_mission_index(cmd.param1);
@@ -1114,7 +1114,6 @@ void
 Navigator::publish_mission_result()
 {
 	_mission_result.timestamp = hrt_absolute_time();
-	_mission_result.instance_count = _mission_instance_count;
 
 	/* lazily publish the mission result only once available */
 	if (_mission_result_pub != nullptr) {