anchor.diff:  
     Offset _calculateOverlayPosition(double width, BuildContext context) {
       final overlayBox =
  -        Overlay.of(context).context.findRenderObject() as RenderBox;
  +        Overlay.of(context)!.context.findRenderObject() as RenderBox;
       final box = context.findRenderObject() as RenderBox;
   
       final maxX = overlayBox.size.width - width;
  
positive.code:   final IconData icon;
  
    /// The minimum screen width for which this button should include text.
    final double minScreenWidthForTextBeforeScaling;
  
    /// Extensions to be surfaced as checkbox settings in the overlay.
    final List<ToggleableServiceExtensionDescription> extensions;
  
negative.code:     _extensionStates = List.filled(widget.extensions.length, false);
      for (int i = 0; i < widget.extensions.length; i++) {
        final extension = widget.extensions[i];
        final state = serviceManager.serviceExtensionManager!
            .getServiceExtensionState(extension.extension);
        _extensionStates[i] = state.value.enabled;
        // Listen for extension state changes so that we can update the value of
  