Handle Dispose exceptions

[boukenka]

Proposal to intercept exceptions when disposing components.
Adding checks for null and try/catch in Dispose methods and during Rendering.
Below is an exception example to be handled.

[ERR] Unhandled exception in circuit 'dQIPK23O_RFuJINsK-Aq9BIEWyzyITdAq6VK6OW-ZSc'.
Microsoft.JSInterop.JSDisconnectedException: JavaScript interop calls cannot be issued at this time. 
This is because the circuit has disconnected and is being disposed.
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.JSRuntimeExtensions.InvokeVoidAsync(IJSRuntime jsRuntime, String identifier, Object[] args)
at Blazor.Diagrams.Extensions.JSRuntimeExtensions.UnobserveResizes(IJSRuntime jsRuntime, ElementReference element)
at Blazor.Diagrams.Components.DiagramCanvas.DisposeAsync()
at Microsoft.AspNetCore.Components.RenderTree.Renderer.<>c__DisplayClass93_0.
<<Dispose>g__HandleAsyncExceptions|0>d.MoveNext()