ArgumentNullException when dynamically adding/removing root components from BlazorWebView

[rhirtz-ores]

Description

While trying to dynamically swap components into an already loaded BlazorWebView I stumbled upon an ArgumentNullException preventing me from altering webview components.

This error is triggered in BlazorWebViewHandler.cs line 119-120. NotifyCollectionChangedEventArgs NewItems/OldItems properties values are casted to RootComponent type regardless of the action operated on the collection.
But the NewItems property will be null when we remove an existing element and OldItems null when we add a new one.

Steps to Reproduce

1. Create a .Net Maui Blazor Hybrid App
2. In MainPage.xaml, put the BlazorWebView in a StackLayout, give BlazorWebView a size, and add a Button with a Click event like so:

    <StackLayout>
        <BlazorWebView x:Name="blazorWebView" HostPage="wwwroot/index.html" WidthRequest="200" HeightRequest="200">
            <BlazorWebView.RootComponents>
                <RootComponent Selector="#app" ComponentType="{x:Type local:Components.Routes}" />
            </BlazorWebView.RootComponents>
        </BlazorWebView>

        <Button Text="Remove webview content" Clicked="OnClick"></Button>
    </StackLayout>

4. In MainPage.xaml.cs code behind implement Click event handler like so:

        public void OnClick(object? sender, EventArgs e)
        {
            blazorWebView.RootComponents.RemoveAt(0);
        }

5. Launch the app and click the button

Result: ArgumentNullException is thrown and BlazorWebView component is still displayed

Link to public reproduction project repository

No response

Version with bug

8.0.71 SR7.1

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Windows

Affected platform versions

windows 10.0.19041.0

Did you find any workaround?

No response

Relevant log output

Eception stack trace:

   at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument) in System.Linq\ThrowHelper.cs:line 10
   at System.Linq.Enumerable.Cast[TResult](IEnumerable source) in System.Linq\Enumerable.cs:line 4278
   at Microsoft.AspNetCore.Components.WebView.Maui.BlazorWebViewHandler.<>c__DisplayClass16_0.<<OnRootComponentsCollectionChanged>b__0>d.MoveNext() in Microsoft.AspNetCore.Components.WebView.Maui\BlazorWebViewHandler.cs:line 113
   at Microsoft.Maui.Dispatching.DispatcherExtensions.<>c__DisplayClass3_0.<<DispatchAsync>b__0>d.MoveNext()
   at Microsoft.Maui.Dispatching.DispatcherExtensions.<>c__DisplayClass2_0`1.<<DispatchAsync>b__0>d.MoveNext()

[Zhanglirong-Winnie]

This issue has been verified Visual Studio 17.13 Preview 2.1 (9.0.30 & 9.0.0 & 8.0.71 &8.0.60). Can repro this issue on windows platform.