Disposal errors when navigating away from `Paint.razor` under some conditions

[Aaronontheweb]

System.NullReferenceException: Object reference not set to an instance of an object.
   at Akka.Actor.ActorRefImplicitSenderExtensions.Tell(IActorRef receiver, Object message)
   at DrawTogether.Components.Pages.Paint.DisposeAsync() in C:\Repositories\Petabridge\DrawTogether.NET\src\DrawTogether\Components\Pages\Paint.razor:line 238
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.<>c__DisplayClass93_0.<<Dispose>g__HandleAsyncExceptions|0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.<>c__DisplayClass93_0.<<Dispose>g__HandleAsyncExceptions|0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.DisposeAsync()
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.<DisposeAsync>g__Await|26_0(Int32 i, ValueTask vt, List`1 toDispose)
   at Microsoft.AspNetCore.Http.Features.RequestServicesFeature.<DisposeAsync>g__Awaited|9_0(RequestServicesFeature servicesFeature, ValueTask vt)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpProtocol.<FireOnCompleted>g__ProcessEvents|242_0(HttpProtocol protocol, Stack`1 events)