fix: navigation to "/" crashes with FluentNavMenu

[Narvalex]

🐛 Bug Report

Whenever you navigate to a sub route and then return to the "/" route FluentNavMenu crashes. It seems that even thought the FluentNavMenu unsubscribes from the NavigationManager and is disposed, it stills receives the LocationChanged event.

💻 Repro or Code Sample

• Clone this repo
• Go to a subroute, like "/counter" using FluentNavMenu
• Return to the home route, the "/" url.

🤔 Expected Behavior

You should return to the home route without any error being thrown.

😯 Current Behavior

An unhandled exception is being thrown.

💁 Possible Solution

This only hapens when the MainLayout component disposes.
Adding the Navigating component to the Router one enables this bug.

<Router AppAssembly="@typeof(App).Assembly">
    <Navigating>
        <!-- Lazy loading... -->
        <div>
            <p>The requested page is loading...</p>
        </div>
    </Navigating>
    <Found Context="routeData">
        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
    </Found>
    <NotFound>
        <PageTitle>Not found</PageTitle>
        <LayoutView Layout="@typeof(MainLayout)">
            <p role="alert">Sorry, there's nothing at this address.</p>
        </LayoutView>
    </NotFound>
</Router>

If you remove the Navigating component the bug will disappear since the MainLayout will not be disposed and only once instance and subscription to OnLocationChanged will be set.

🔦 Context

I just wanted to have a NavMenu. It was hard to detect that the Navigating component will make the MainLayout unmount for every route change. This route changing seems to enable a race condition when the NavigationManager pushes an event to an already disposed FluentNavMenu that was stripped of its menu items when was disposed.

🌍 Your Environment

.NET 7, on Windows 11 with the FluentUI 3.1.0