Fix position setpoint update logic in Mission RTL

Currently, when proceeding to the landing point the previous setpoint is not updated, which results in an unexpected and off course landing pattern in fixed wing. (see #25436)

src/modules/navigator/rtl_direct_mission_land.cpp

@@ -203,10 +203,10 @@ void RtlDirectMissionLand::setActiveMissionItems()
 
 			_mission_item.autocontinue = true;
 			_mission_item.time_inside = 0.0f;
-
-			pos_sp_triplet->previous = pos_sp_triplet->current;
 		}
 
+		pos_sp_triplet->previous = pos_sp_triplet->current;
+
 		if (num_found_items > 0) {
 			mission_item_to_position_setpoint(next_mission_items[0u], &pos_sp_triplet->next);
 		}