title: Flutter null safety issues, unable to compile
body: <p>I am having the following errors when building my FLUTTER WEB application:</p>
  <pre><code>Error: Cannot run with sound null safety, because the following dependencies don't support null safety:
  
   - package:html2md
   - package:html
   - package:csslib
  
  For solutions, see https://dart.dev/go/unsound-null-safety ../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart:61:5: Warning: Operand of null-aware operation '?.' has type 'EasyWebView' which excludes null.
   - 'EasyWebView' is from 'package:easy_web_view/src/web.dart' ('../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart').
      widget?.onLoaded();
      ^ ../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart:66:15: Warning: Operand of null-aware operation '?.' has type 'EasyWebView' which excludes null.
   - 'EasyWebView' is from 'package:easy_web_view/src/web.dart' ('../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart').
            if (widget?.onLoaded != null) {
                ^ ../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart:95:14: Warning: Operand of null-aware operation '?.' has type 'EasyWebView' which excludes null.
   - 'EasyWebView' is from 'package:easy_web_view/src/web.dart' ('../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart').
        width: widget?.width,
               ^ ../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart:96:15: Warning: Operand of null-aware operation '?.' has type 'EasyWebView' which excludes null.
   - 'EasyWebView' is from 'package:easy_web_view/src/web.dart' ('../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart').
        height: widget?.height,
                ^ ../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart:124:20: Warning: Operand of null-aware operation '?.' has type 'EasyWebView' which excludes null.
   - 'EasyWebView' is from 'package:easy_web_view/src/web.dart' ('../../../flutter/.pub-cache/hosted/pub.dartlang.org/easy_web_view-1.4.0-nullsafety/lib/src/web.dart').
                key: widget?.key,
                     ^ Unhandled exception: Bad state: Unsupported Null Safety mode NonNullableByDefaultCompiledMode.Invalid, in null.
  #0      ProgramCompiler.emitModule (package:dev_compiler/src/kernel/compiler.dart:435:9)
  #1      JavaScriptBundler.compile (package:frontend_server/src/javascript_bundle.dart:144:33)
  #2      FrontendCompiler.writeJavascriptBundle (package:frontend_server/frontend_server.dart:632:20) &lt;asynchronous suspension&gt;
  #3      FrontendCompiler.compile (package:frontend_server/frontend_server.dart:545:9) &lt;asynchronous suspension&gt;
  #4      listenAndCompile.&lt;anonymous closure&gt; (package:frontend_server/frontend_server.dart:1105:11) &lt;asynchronous suspension&gt; Finished with error: the Dart compiler exited unexpectedly. Failed to compile application.
  </code></pre>
  <p>The following are my dependencies:</p>
  <pre><code>  cupertino_icons: ^1.0.2
    http: ^0.13.1
    json_annotation: ^4.0.1
    provider: ^5.0.0
    google_fonts: ^2.0.0
    vibration: ^1.7.4-nullsafety.0 #^1.7.4
    firebase_core: ^1.0.2
    cloud_firestore: ^1.0.2
    easy_web_view: ^1.4.0-nullsafety #easy_web_view: ^1.3.0
    intl: ^0.17.0
    uuid: ^3.0.2
    url_launcher: ^6.0.2
    shared_preferences: ^2.0.5
  </code></pre>