我尝试使用flutter build web在发布模式下构建flutter web应用程序（也尝试过flutter build web --no-sound-null-safety）。当我这样做时，我得到下面的错误。

D:\saves\reset_password>flutter build web

Building without sound null safety
For more information see https://dart.dev/null-safety/unsound-null-safety

Target dart2js failed: Exception: Warning: The 'dart2js' entrypoint script is deprecated, please use 'dart compile js' instead.
.dart_tool/flutter_build/1916f9367c0e6ad6c929bd88cf5227e5/web_plugin_registrant.dart:14:38:
Error: Null safety features are disabled for this library.
void registerPlugins([final Registrar? pluginRegistrar]) {
                                     ^
Error: Compilation failed.

Compiling lib\main.dart for the Web...                             44.9s
Exception: Failed to compile application for the Web.

当我使用flutter run直接在调试模式下运行它时，它工作正常。我最近升级到flutter 3. 0和im使用Android studio。下面是我的flutter doctor（我知道android工具丢失了。因为我是为web构建的，所以我没有太注意它）

D:\saves\reset_password>flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel master, 3.1.0-0.0.pre.966, on Microsoft Windows [Version 10.0.19044.1706], locale en-IN)
[!] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    X cmdline-tools component is missing
      Run `path/to/sdkmanager --install "cmdline-tools;latest"`
      See https://developer.android.com/studio/command-line for more details.
    X Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
      See https://flutter.dev/docs/get-started/install/windows#android-setup for more details.
[√] Chrome - develop for the web
[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.8.5)
[√] Android Studio (version 4.1)
[√] VS Code (version 1.66.2)
[√] Connected device (3 available)
[√] HTTP Host Availability

! Doctor found issues in 1 category.