newInstance method Null safety

Implementation

static Future<RedditClient> newInstance() async{
  final client = RedditClient._();

  FlutterSecureStorage storage = const FlutterSecureStorage();
  String? credential = await storage.read(key: "redditCredentials");
  if (credential == null) {
    await client._useReadOnlyClient();
    return client;
  }
  client._reddit = Reddit.restoreInstalledAuthenticatedInstance(
    credential,
    clientId: await rootBundle.loadString("assets/draw.ini"),
    userAgent: "soreo"
  );
  client._state = AuthenticationStatus.authenticated;
  return client;
}