MPC_POS_MODE remove old metadata and explicitly handle invalid configuration

src/modules/flight_mode_manager/FlightModeManager.cpp

@@ -314,6 +314,12 @@ void FlightModeManager::start_flight_task()
 
 		case 4:
 		default:
+			if (_param_mpc_pos_mode.get() != 4) {
+				PX4_ERR("MPC_POS_MODE %d invalid, resetting", _param_mpc_pos_mode.get());
+				_param_mpc_pos_mode.set(4);
+				_param_mpc_pos_mode.commit();
+			}
+
 			error = switchTask(FlightTaskIndex::ManualAcceleration);
 			break;
 		}