fix: Error on dispose in FluentMenu

[JamesNK]

🐛 Bug Report

I see this error when hot reloading:

fail: Aspire.Hosting.Dashboard.Microsoft.AspNetCore.Components.Server.Circuits.CircuitHost[111]
      Unhandled exception in circuit 'rBZiMW0JBoyiB3tlk6cZbCzTCjG4stihwH9QbT2x3k4'.
      System.ArgumentNullException: Value cannot be null. (Parameter 'jsObjectReference')
         at System.ArgumentNullException.Throw(String paramName)
         at System.ArgumentNullException.ThrowIfNull(Object argument, String paramName)
         at Microsoft.JSInterop.JSObjectReferenceExtensions.InvokeVoidAsync(IJSObjectReference jsObjectReference, String identifier, Object[] args)
         at Microsoft.FluentUI.AspNetCore.Components.FluentMenu.DisposeAsync()

🤔 Expected Behavior

No error

😯 Current Behavior

Error

💁 Possible Solution

Check whether these module references are null before using them:

fluentui-blazor/src/Core/Components/Menu/FluentMenu.razor.cs

Lines 400 to 402 in 948540e

	await _jsModule.InvokeVoidAsync("dispose", Anchor);
	await _jsModule.DisposeAsync();
	await _anchoredRegionModule.DisposeAsync();

IMO the fields should be nullable so nullable checks catch this. Almost everywhere they're used in this type they're checked for null before use.

🔦 Context

🌍 Your Environment

• OS & Device: [e.g. MacOS, iOS, Windows, Linux] on [iPhone 7, PC]
• Browser [e.g. Microsoft Edge, Google Chrome, Apple Safari, Mozilla FireFox]
• .NET and Fluent UI Blazor library Version [e.g. 8.0.2 and 4.4.1]

[MarvinKlein1508]

I'm reopening this issue because I ran into a similiar issue. So I tried the latest pre-release version which indeed fixes the null exception in the dispose but now I'm getting this error here:

[2025-10-21T10:38:57.619Z] Error: System.ObjectDisposedException: Cannot access a disposed object.

Object name: 'Microsoft.JSInterop.DotNetObjectReference`1[[Microsoft.FluentUI.AspNetCore.Components.FluentMenu, Microsoft.FluentUI.AspNetCore.Components, Version=4.13.1.25290, Culture=neutral, PublicKeyToken=null]]'.

   at Microsoft.JSInterop.JSRuntime.TrackObjectReference[TValue](DotNetObjectReference`1 dotNetObjectReference)

   at Microsoft.JSInterop.Infrastructure.DotNetObjectReferenceJsonConverter`1.Write(Utf8JsonWriter writer, DotNetObjectReference`1 value, JsonSerializerOptions options)

   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)

   at System.Text.Json.Serialization.JsonConverter`1.TryWriteAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)

   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)

   at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryWrite(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, WriteStack& state)

   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)

   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)

   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)

   at System.Text.Json.JsonSerializer.WriteString[TValue](TValue& value, JsonTypeInfo`1 jsonTypeInfo)

   at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, CancellationToken cancellationToken, Object[] args)

   at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, Object[] args)

   at Microsoft.JSInterop.JSObjectReferenceExtensions.InvokeVoidAsync(IJSObjectReference jsObjectReference, String identifier, Object[] args)

   at Microsoft.FluentUI.AspNetCore.Components.FluentMenu.OnAfterRenderAsync(Boolean firstRender) in /_/src/Core/Components/Menu/FluentMenu.razor.cs:line 245

   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

Unfortunately I don't know how to reproduce the issue yet.

[MarvinKlein1508]

I think this has something todo with dynamic content. In my solution a FluentMenu is added to each row within an HTML table. When I filter this table the rows will be removed or rendered and then the app crashes with the exception above. I try to craft together a working solution to re-create the issue.