title: is there a way to fix list widget eror
body: <pre><code>
  class ProgressHUD extends StatelessWidget {
    final Widget child;
    final bool inAsyncCall;
    final double opacity;
    final Color color;
    final Animation&lt;Color&gt; valueColor;
  
    ProgressHUD({
      Key key,
      @required this.child,
      @required this.inAsyncCall,
      this.color = Colors.grey,
      this.opacity = 0.3,
      this.valueColor,
    }) : super(key: key);
  
    @override
    Widget build(BuildContext context) {
      List&lt;Widget&gt; widgetList = new List&lt;Widget&gt;();
      widgetList.add(child);
      if (inAsyncCall) {
        final modal = new Stack(
          children: [
            new Opacity(
              opacity: opacity,
              child: ModalBarrier(
                dismissible: false,
                color: color,
              ),
            ),
            new Center(
              child: new CircularProgressIndicator(),
            ),
          ],
        );
        widgetList.add(modal);
      }
      return Stack(
        children: [],
      );
    }
  }
  </code></pre>
  <p>I did this but it keeps showing this error:</p>
  <p>'List' is deprecated and shouldn't be used. Use a list literal, [], or the List.filled constructor instead.
  Try replacing the use of the deprecated member with the replacement.</p>