System.NullReferenceException: Object reference not set to an instance of an object. when opening the metrics view

[devurandom]

When I click on "Metrics" (navigate to http://localhost:8080/metrics) the page does not load and I see the following console output from dotnet run:

warn: Microsoft.AspNetCore.Components.Server.Circuits.RemoteRenderer[100]
      Unhandled exception rendering component: Object reference not set to an instance of an object.
      System.NullReferenceException: Object reference not set to an instance of an object.
         at OTLPView.Pages.Metrics.<BuildRenderTree>b__21_14(RenderTreeBuilder __builder6) in [REDACTED]/OTLPView/OTLPView/Pages/Metrics.razor:line 69
         at Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddContent(Int32 sequence, RenderFragment fragment)
         at MudBlazor.MudCardContent.BuildRenderTree(RenderTreeBuilder __builder)
         at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)
fail: Microsoft.AspNetCore.Components.Server.Circuits.CircuitHost[111]
      Unhandled exception in circuit 'XG7FWGQ_qSEIoAnEvNRqtGMaoLuxmCgAliH-y9PPJ-I'.
      System.NullReferenceException: Object reference not set to an instance of an object.
         at OTLPView.Pages.Metrics.<BuildRenderTree>b__21_14(RenderTreeBuilder __builder6) in [REDACTED]/OTLPView/OTLPView/Pages/Metrics.razor:line 69
         at Microsoft.AspNetCore.Components.Rendering.RenderTreeBuilder.AddContent(Int32 sequence, RenderFragment fragment)
         at MudBlazor.MudCardContent.BuildRenderTree(RenderTreeBuilder __builder)
         at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)

In case this error is caused by my local changes: I had to patch OTLPView to make it run on my machine, see:

• System.IO.IOException: Failed to bind to address https://[::]:4317: address already in use. with default settings #11
• Option to serve HTTP instead of HTTPS #12