Storing base 64 locally and use it offline - flutter

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.