title: When I build the Web using FlexibleSpaceBar and check it on the web, not the tool, it is grayed out
body: <p>I used FlexibleSpaceBar with flutter web.
  If I run it in Visual Studio code, it works normally.
  However, when I build it on the web and check it, the widget is grayed out as shown in the picture.</p>
  <p>Android and IOS builds are working fine.
  It is the same when building and deploying firebase hosting and running the simulator.</p>
  <p>Any other workarounds for the web?</p>
  <p>Advice from seniors please.</p>
  <ul>
  <li><p>[✓] Flutter (Channel stable, 2.2.2, on Mac OS X 10.15.7 19H2
  darwin-x64, locale ko-KR)</p>
  <p>[✓] Android toolchain - develop for Android devices (Android SDK
  version 30.0.2)</p>
  <p>[✓] Xcode - develop for iOS and macOS</p>
  <p>[✓] Chrome - develop for the web</p>
  <p>[✓] Android Studio (version 4.1)</p>
  </li>
  </ul>
  <p><a href="https://i.stack.imgur.com/2ppOm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2ppOm.png" alt="enter image description here" /></a></p>
  <pre><code>void main() {
    runApp(MyApp());
  }
  
  class MyApp extends StatelessWidget {
    // This widget is the root of your application.
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: Test(),
      );
    }
  }
  
  class Test extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        body: DefaultTabController(
          length: 2,
          child: NestedScrollView(
            headerSliverBuilder: (context, value) {
              return [
                SliverAppBar(
                  floating: true,
                  pinned: true,
                  bottom: TabBar(
                    tabs: [
                      Tab(text: &quot;Posts&quot;),
                      Tab(text: &quot;Likes&quot;),
                    ],
                  ),
                  expandedHeight: 450,
                  flexibleSpace: FlexibleSpaceBar(
                    collapseMode: CollapseMode.pin,
                    background: Container(
                      color: Colors.purple,
                      height: 300,
                    ), // This is where you build the profile part
                  ),
                ),
              ];
            },
            body: TabBarView(
              children: [
                Container(
                  child: ListView.builder(
                    itemCount: 100,
                    itemBuilder: (context, index) {
                      return Container(
                        height: 40,
                        alignment: Alignment.center,
                        color: Colors.lightBlue[100 * (index % 9)],
                        child: Text('List Item $index'),
                      );
                    },
                  ),
                ),
                Container(
                  child: ListView.builder(
                    itemCount: 100,
                    itemBuilder: (context, index) {
                      return Container(
                        height: 40,
                        alignment: Alignment.center,
                        color: Colors.lightBlue[100 * (index % 9)],
                        child: Text('List Item $index'),
                      );
                    },
                  ),
                ),
              ],
            ),
          ),
        ),
      );
    }
  }
  </code></pre>