anchor.diff:  /// This is a ListView of text lines, with a monospace font and a border.
   class _ConsoleOutput extends StatefulWidget {
     const _ConsoleOutput({
  -    Key key,
  -    @required this.lines,
  +    Key? key,
  +    required this.lines,
       this.footer,
     }) : super(key: key);
   
     final ValueListenable<List<ConsoleLine>> lines;
   
  -  final Widget footer;
  +  final Widget? footer;
   
     @override
     _ConsoleOutputState createState() => _ConsoleOutputState();
  
positive.code: 
      if (_scrollToBottom) {
        _scrollToBottom = false;
        WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
          if (_scroll.hasClients) {
            _scroll.autoScrollToBottom();
          } else {
  
negative.code:     return Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          if (title != null) title!,
          Expanded(
            child: Material(
              child: Stack(
                children: [
                  child,
                  if (controls.isNotEmpty)
                    _ConsoleControls(
                      controls: controls,
                    ),
  