title: Flutter - Error: Null safety features are disabled for this library
body: <p>I have been working on a flutter project for a long time. Now I have set up my new laptop and after reinstalling the tools for VS Code(Flutter, Android Studio) I face the error mentioned in the title of this question.</p>
  <pre><code>Error: Null safety features are disabled for this library.
  Try removing the package language version or setting the language version to 2.10 or higher.
  </code></pre>
  <p>As advised, I have set my flutter-sdk version to &gt;= 2.10.0 but it is still not working.
  To enable the NNBD I would have to enable experimental support but people advise against it until it is fully released. So what should I do to get my codebase working? Enable NNBD experimental support or is there any other solution?
  Here is my flutter doctor:</p>
  <pre><code>[√] Flutter (Channel stable, 1.22.3, on Microsoft Windows [Version 10.0.19041.572], locale en-AT)
      • Flutter version 1.22.3 at C:\flutter
      • Framework revision 8874f21e79 (6 days ago), 2020-10-29 14:14:35 -0700
      • Engine revision a1440ca392
      • Dart version 2.10.3
  
   
  [!] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
      • Android SDK at C:\Users\xyz\AppData\Local\Android\sdk
      • Platform android-30, build-tools 30.0.2
      • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
      • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
      ! Some Android licenses not accepted.  To resolve this, run: flutter doctor --android-licenses
  
  [!] Android Studio (version 4.1.0)
      • Android Studio at C:\Program Files\Android\Android Studio
      X Flutter plugin not installed; this adds Flutter specific functionality.
      X Dart plugin not installed; this adds Dart specific functionality.
      • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
  
  [√] VS Code (version 1.50.1)
      • VS Code at C:\Users\xyz\AppData\Local\Programs\Microsoft VS Code
      • Flutter extension version 3.16.0
  
  [√] Connected device (1 available)
      • Android SDK built for x86 (mobile) • emulator-5554 • android-x86 • Android 8.0.0 (API 26) (emulator)
  
  ! Doctor found issues in 2 categories.
  </code></pre>
  <p>If needed, I will provide extra information/logs/files.</p>