Fix some deprecation warnings

lib/main.dart

@@ -101,7 +101,6 @@ class _MyHomePageState extends State<MyHomePage> {
       );
 
       final uptime = await client.run('uptime');
-      print(uptime);
       setState(() {
         _output = utf8.decode(uptime);
       });
@@ -387,7 +386,7 @@ class _MyHomePageState extends State<MyHomePage> {
       return mainPage;
     }
 
-    var title;
+    Widget title;
     var children = <Widget>[];
     var actions = [
       TextButton(onPressed: authentikApiState.exit, child: Text("Cancel")),
@@ -472,9 +471,6 @@ class AuthentikUserSettingsChangeDialogState extends ChangeNotifier {
   List<String> get keysToKeep => _keysToKeep;
 
   Future<oauth2.Client?> getOAuth2Client() async {
-    // This is a placeholder for OAuth2 client initialization.
-    // Replace with your actual OAuth2 client setup.
-
     final authorizationEndpoint = Uri.parse(
       'https://auth.leinelab.org/application/o/authorize/',
     );
@@ -484,23 +480,10 @@ class AuthentikUserSettingsChangeDialogState extends ChangeNotifier {
     );
 
     final identifier = 'UwSMm8gTwBTUURSaxp5uPpuwX1OkGO4FRHeO9v3i';
-    final secret = null; // = 'my client secret';
+    final secret = null;
 
     final redirectUrl = Uri.parse('http://localhost:30165/');
 
-    // final credentialsFile = File('~/.myapp/credentials.json');
-
-    // //....
-
-    // var exists = await credentialsFile.exists();
-
-    // if (exists) {
-    //   var credentials = oauth2.Credentials.fromJson(
-    //     await credentialsFile.readAsString(),
-    //   );
-    //   return oauth2.Client(credentials, identifier: identifier, secret: secret);
-    // }
-
     var grant = oauth2.AuthorizationCodeGrant(
       identifier,
       authorizationEndpoint,
@@ -513,18 +496,19 @@ class AuthentikUserSettingsChangeDialogState extends ChangeNotifier {
       scopes: ["profile", "email", "goauthentik.io/api", "openid"],
     );
 
-    // TODO: clicking the button twice might try to bind the server twice
     server = await HttpServer.bind("127.0.0.1", 30165);
 
     await launchUrl(authorizationUrl);
 
-    var queryParameters;
-
     if (server == null) {
       // exit() might have been called before we arrived here.
       return null;
     }
 
+    // When the http server receives a request, we store the query parameters,
+    // so the oauth2 client can handle the response.
+    Map<String, String>? queryParameters;
+
     await server!.forEach((HttpRequest request) {
       request.response.write(
         'Success! You can close this window now and go back to the app.',
@@ -534,7 +518,12 @@ class AuthentikUserSettingsChangeDialogState extends ChangeNotifier {
       server!.close();
     });
 
-    return await grant.handleAuthorizationResponse(queryParameters);
+    if (queryParameters == null) {
+      // If we did not receive any query parameters, exit
+      return null;
+    }
+
+    return await grant.handleAuthorizationResponse(queryParameters!);
   }
 
   Future<void> start(String currentKey) async {
@@ -682,13 +671,13 @@ class KeepOrDeleteKey extends StatelessWidget {
         );
 
     final buttonStyleKeepActive = ButtonStyle(
-      backgroundColor: MaterialStateProperty.all(Colors.blue),
-      foregroundColor: MaterialStateProperty.all(Colors.white),
+      backgroundColor: WidgetStateProperty.all(Colors.blue),
+      foregroundColor: WidgetStateProperty.all(Colors.white),
     );
 
     final buttonStyleDeleteActive = ButtonStyle(
-      backgroundColor: MaterialStateProperty.all(Colors.red),
-      foregroundColor: MaterialStateProperty.all(Colors.white),
+      backgroundColor: WidgetStateProperty.all(Colors.red),
+      foregroundColor: WidgetStateProperty.all(Colors.white),
     );
 
     ButtonStyle? buttonStyleKeep;