Storing base 64 locally and use it offline

Question

I have a 64 base image that am getting from my database , which I want to store locally and reuse offline. am using local storage package , the image works perfectly fine when I call it online but fades away offline . here is where am storing it :

String baseUrl = await GetSharedPrefs.getBaseURl();
    _imageLogoPath =
        (await SettingsServices().fetchLogoImage(baseUrl: baseUrl, id: 1));
         storage.setItem('logoImage', _imageLogoPath);
       
    notifyListeners();

and this is where am calling it :

class _LogoViewState extends State<Logo> {
  void initState() {
    Provider.of<SettingsViewModel>(context, listen: false).fetchLogoPath();

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    final LocalStorage storage = new LocalStorage('deepnrise');
    var settings = Provider.of<SettingsViewModel>(context);
    String? image = settings.imagepath;
    int i = 1;

    String im = storage.getItem('logoImage');
    
    if (im!.isNotEmpty) {
      i +=1;
      print("soy image $im");
      final UriData? data = Uri.parse(im).data;
      print(image);
      Uint8List? myImage = data?.contentAsBytes();
      return Padding(
        padding: EdgeInsets.all(10.0),
        child: ClipRRect(
            borderRadius: BorderRadius.circular(15),
            child: Image.memory(
              myImage!,
              fit: BoxFit.contain,
              width: 50,
            )),
      );
    } else if (im.isEmpty || im == null) {
      return Padding(
        padding: EdgeInsets.all(16.0),
        child: ClipRRect(
            borderRadius: BorderRadius.circular(15),
            child: Image.asset(
              "assets/images/deepn.png",
              fit: BoxFit.contain,
              width: 35,
            )),
      );
    }
    return Padding(
      padding: EdgeInsets.all(16.0),
      child: ClipRRect(
          borderRadius: BorderRadius.circular(15),
          child: Image.asset(
            "assets/images/deepn.png",
            fit: BoxFit.contain,
            width: 35,
          )),
    );
  }
}

every time I get a null exception (null is not subtype of type string) , so I tried to call my provider in another widget , which resulted in the image fading away when offline . I want to be able to call the image from local storage , when off/ online . I have tried shared preferences package and the same thing happens if anyone please know how to help don't hesitate thanks in advance.