FlightTaskAuto: reset lock position to NAN

src/lib/FlightTasks/tasks/FlightTaskAuto.cpp

@@ -126,6 +126,7 @@ bool FlightTaskAuto::_evaluateTriplets()
 		} else {
 			target(0) = _lock_position_xy(0);
 			target(1) = _lock_position_xy(1);
+			_lock_position_xy *= NAN;
 		}
 
 	} else {

src/lib/FlightTasks/tasks/FlightTaskAuto.hpp

@@ -85,7 +85,7 @@ protected:
 	uORB::Subscription<home_position_s> *_sub_home_position{nullptr};
 
 private:
-	matrix::Vector2f _lock_position_xy{};
+	matrix::Vector2f _lock_position_xy{NAN, NAN};
 
 	uORB::Subscription<position_setpoint_triplet_s> *_sub_triplet_setpoint{nullptr};