Fix: disposed _reference in OnAfterRenderAsync

[SKuckluck]

Found via StackTrace that _reference was able to be disposed when OnAfterRenderAsync was called

Message: Cannot access a disposed object.
Object name: 'DotNetObjectReference`1'.
StackTrace:    at Microsoft.JSInterop.DotNetObjectReference`1.ThrowIfDisposed()
   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.Converters.ArrayConverter`2.OnWriteResume(Utf8JsonWriter writer, TElement[] array, 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.JsonSerializer.WriteUsingSerializer[TValue](Utf8JsonWriter writer, TValue& value, JsonTypeInfo jsonTypeInfo)
   at System.Text.Json.JsonSerializer.WriteStringUsingSerializer[TValue](TValue& value, JsonTypeInfo 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.JSRuntimeExtensions.InvokeVoidAsync(IJSRuntime jsRuntime, String identifier, Object[] args)
   at Blazor.Diagrams.Extensions.JSRuntimeExtensions.ObserveResizes[T](IJSRuntime jsRuntime, ElementReference element, DotNetObjectReference`1 reference)
   at Blazor.Diagrams.Components.DiagramCanvas.OnAfterRenderAsync(Boolean firstRender)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

[zHaytam]

Hello, in what case does this happen?

[SKuckluck]

Hi, my bad for not explaning further.

I was copying an object from a canvas, reload the page with F5 and then tried to paste the same object on the same canvas.

Never ran into this problem without reloading. Only ran into it twice till now. Most of the time it works fine.

[zHaytam]

Can you please fix the issues? PRs need to be targeted to develop not master

[zHaytam]

Also, can you tell me how are you copying the object and pasting it?