Sample code error on web platform

[tilongzs]

The following sample code is fine in Windows(desktop) platform, but it reports an error in web (Edge) platform.
Off topic, is this project still going to be updated?The library 'package:notifier_plugin/notifier_plugin.dart' is legacy, and shouldn't be imported into a null safe library.

import 'package:flutter/material.dart';
import 'package:notifier_plugin/notifier_plugin.dart';

ValNotifier countN = ValNotifier(initialVal: 0);

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _MyAppState();
  }
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'App',
      initialRoute: '/',
      routes: {
        '/': (context) => HomePage(),
      },
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _HomePageState();
  }
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    print('build');

    return Scaffold(
      appBar: AppBar(title: Text('notifier_plugin')),
      body: Column(
        children: [
          countN - (count)=> Text(count.toString()),
          ElevatedButton(onPressed: () => countN(countN.val+1), child: Text("Click Me")),
        ],
      ),
    );
  }
}

Flutter Web Bootstrap: Programmatic
build

======== Exception caught by widgets library =======================================================
The following JSRangeError was thrown building KeyedSubtree-[GlobalKey#ece68]:
Invalid argument: Maximum call stack size exceeded

The relevant error-causing widget was:
Scaffold Scaffold:file:///D:/SoftwareDev/flutter/HelloWorld/lib/main.dart:42:12
When the exception was thrown, this was the stack:
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/classes.dart 304:22 getMethods
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/classes.dart 347:11 getMethodType
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 55:39 bind
...