Fatal Exception: io.flutter.plugins.firebase.crashlytics.FlutterError: PlatformException(writeCharacteristic, device is disconnected, null, null)
       at StandardMethodCodec.decodeEnvelope(message_codecs.dart:653)
       at MethodChannel._invokeMethod(platform_channel.dart:367)
       at FlutterBluePlus._invokeMethod(flutter_blue_plus.dart:614)
       at BluetoothCharacteristic.write(bluetooth_characteristic.dart:204)
       at BleTransport.writeCharacteristic(ble_transport.dart:191)
       at CustomDeviceConnection._sendCommand(custom_connection.dart:81)
       at CustomDeviceConnection.performRetrieveBatteryLevel(custom_connection.dart:92)
       at DeviceConnection.retrieveBatteryLevel(device_connection.dart:182)
       at DeviceProvider._onDeviceConnected(device_provider.dart:334)

          Fatal Exception: FlutterError
0  ???                            0x0 BluetoothCharacteristic.write + 171 (bluetooth_characteristic.dart:171)
1  ???                            0x0 BleTransport.writeCharacteristic + 191 (ble_transport.dart:191)
2  ???                            0x0 CustomDeviceConnection._sendCommand + 81 (custom_connection.dart:81)
3  ???                            0x0 CustomDeviceConnection.performRetrieveBatteryLevel + 92 (custom_connection.dart:92)
4  ???                            0x0 CustomDeviceConnection.performGetBleBatteryLevelListener.<fn> + 112 (custom_connection.dart:112)