I am running on web and getting this error. Error: MissingPluginException(No implementation found for method close on channel flutter_webview_plugin)

## System info

Issue occurs on: WEB
Plugin version: latest
Flutter doctor output:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.0, on macOS 11.2.2 20D80 darwin-x64, locale en-PK)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] Connected device (1 available)

• No issues found!

## Steps to Reproduce
Simply just run it on web and the page doesn't load and through an exception.

## Logs

[+4371 ms] Error: MissingPluginException(No implementation found for method close on channel flutter_webview_plugin)
at Object.throw_ [as throw] (http://localhost:53868/dart_sdk.js:5334:11)
at MethodChannel._invokeMethod (http://localhost:53868/packages/flutter/src/services/system_channels.dart.lib.js:954:21)
at _invokeMethod.next ()
at http://localhost:53868/dart_sdk.js:39032:33
at _RootZone.runUnary (http://localhost:53868/dart_sdk.js:38889:58)
at _FutureListener.thenAwait.handleValue (http://localhost:53868/dart_sdk.js:33875:29)
at handleValueCallback (http://localhost:53868/dart_sdk.js:34435:49)
at Function._propagateToListeners (http://localhost:53868/dart_sdk.js:34473:17)
at _Future.new.[_completeWithValue] (http://localhost:53868/dart_sdk.js:34315:23)
at async._AsyncCallbackEntry.new.callback (http://localhost:53868/dart_sdk.js:34338:35)
at Object._microtaskLoop (http://localhost:53868/dart_sdk.js:39176:13)
at _startMicrotaskLoop (http://localhost:53868/dart_sdk.js:39182:13)
at http://localhost:53868/dart_sdk.js:34689:9
[ +6 ms] Error: MissingPluginException(No implementation found for method launch on channel flutter_webview_plugin)
at Object.throw_ [as throw] (http://localhost:53868/dart_sdk.js:5334:11)
at MethodChannel._invokeMethod (http://localhost:53868/packages/flutter/src/services/system_channels.dart.lib.js:954:21)
at _invokeMethod.next ()
at http://localhost:53868/dart_sdk.js:39032:33
at _RootZone.runUnary (http://localhost:53868/dart_sdk.js:38889:58)
at _FutureListener.thenAwait.handleValue (http://localhost:53868/dart_sdk.js:33875:29)
at handleValueCallback (http://localhost:53868/dart_sdk.js:34435:49)
at Function._propagateToListeners (http://localhost:53868/dart_sdk.js:34473:17)
at _Future.new.[_completeWithValue] (http://localhost:53868/dart_sdk.js:34315:23)
at async._AsyncCallbackEntry.new.callback (http://localhost:53868/dart_sdk.js:34338:35)
at Object._microtaskLoop (http://localhost:53868/dart_sdk.js:39176:13)
at _startMicrotaskLoop (http://localhost:53868/dart_sdk.js:39182:13)
at http://localhost:53868/dart_sdk.js:34689:9

Bắt đầu bằng cách tái hiện lỗi với Flutter 2.0.0 trên web và kiểm tra cách plugin xử lý các phương thức close và launch trên nền tảng đó. Công việc được xem là hoàn tất khi trang web được báo cáo tải mà không có lỗi MissingPluginException, với hành vi nền tảng bắt buộc được xác định và được bao phủ bởi một bài kiểm thử phù hợp.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.