NullRef in WriteFast

[BrennanConroy]

New Web App and ran wrk -c 256 -t 32 -d 10 http://10.0.0.1:5000

@davidfowl @halter73

fail: Microsoft.AspNetCore.Server.Kestrel[13]
      Connection id "0HL3FO2QGA3BF": An unhandled exception was thrown by the application.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.PipelineExtensions.WriteFast(WritableBuffer buffer, ReadOnlySpan`1 source)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.Frame.CreateResponseHeader(Byte[] statusBytes, Boolean appCompleted)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.Frame.InitializeResponseAwaited>d__190.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Server.Kestrel.Internal.Http.Frame.<WriteAsyncAwaited>d__180.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternalAsync>d__26.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.<WriteAsync>d__21.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.Internal.PagedBufferedTextWriter.WriteAsync>d__13.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.Internal.ViewBuffer.<WriteToAsync>d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

[davidfowl]

This is likely write after close.

[BrennanConroy]

Yeah, it was happening at the end of a wrk session