anchor.diff:    late final MDCButton editorUiOutputTab;
     late final MDCButton editorConsoleTab;
     late final MDCButton editorDocsTab;
  -  final _nullSafetyEnabled = true;
   
     WorkshopUi() {
       _init();
  
positive.code:     // Set up CodeMirror
      editor = (editorFactory as CodeMirrorFactory)
          .createFromElement(_editorHost, options: codeMirrorOptions)
        ..theme = 'darkpad'
        ..mode = 'dart'
        ..showLineNumbers = true;
  
      context = WorkshopDartSourceProvider(editor);
      docHandler = DocHandler(editor, context);
  
negative.code:       querySelector('#editor-panel-footer') as DivElement;
  
    @override
    bool get nullSafetyEnabled => true;
  
    /// Whether null safety was enabled for the previous execution.
    @override
    bool get nullSafetyWasPreviouslyEnabled => true;
  
    @override
    set nullSafetyEnabled(bool v) {
  