exception was thrown: Null check operator used on a null value

Question

The following _TypeError was thrown building SplashScreen(dirty): Null check operator used on a null value

The relevant error-causing widget was:
  SplashScreen SplashScreen:file:///D:/cek/chat_apps/lib/main.dart:45:43

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Another exception was thrown: Null check operator used on a null value

Another exception was thrown: 'package:flutter/src/material/theme_data.dart': Failed assertion: line 449 pos 12: 'colorScheme?.brightness == null|| brightness == null || colorScheme!.brightness == brightness': is not true.
Lost connection to device.

class MyApp extends StatelessWidget {
  final authC = Get.put(AuthController(), permanent: true);

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: Future.delayed(Duration(seconds: 3)),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.done) {
          return Obx(
            () => GetMaterialApp(
              title: "ChatApp",
              theme: ThemeData(
                primaryColor: Colors.white, colorScheme: ColorScheme.fromSwatch().copyWith(secondary: Colors.black),
              ),
              initialRoute: authC.isSkipIntro.isTrue
                  ? authC.isAuth.isTrue
                      ? Routes.HOME
                      : Routes.LOGIN
                  : Routes.INTRODUCTION,
              getPages: AppPages.routes,
            ),
          );
        }
        return FutureBuilder(
          future: authC.firstInitialized(),
          builder: (context, snapshot) => SplashScreen(),
        );
      },

Answer 1

I think it's related to this condition:

 colorScheme!.brightness == brightness

You need to check beforehand if colorScheme is not null or replace the ! operator with ?.