navigator: when landed only exit idle if mission/takoff

src/modules/mc_pos_control/mc_pos_control_main.cpp

@@ -1605,6 +1605,7 @@ void MulticopterPositionControl::control_auto(float dt)
 
 	} else {
 		/* no waypoint, do nothing, setpoint was already reset */
+		/* we are in idle */
 	}
 }