NullReferenceException in RequestTrackingTelemetryModule.NeedProcessRequest

[AlexBulankou]

Issue reported by error telemetry:
weekly unique ikey count: 43
SDKs: 2.0.0.30671 | 2.1.0.1924 | dotnet: 2.1.0.14852 | w_2.0.0.30671

Error message:
AI (Internal): [msg=HanderFailure];[exception=System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.ApplicationInsights.Web.RequestTrackingTelemetryModule.NeedProcessRequest(HttpContext httpContext)
at Microsoft.ApplicationInsights.Web.RequestTrackingTelemetryModule.OnEndRequest(EventWrittenEventArgs args)
at Microsoft.ApplicationInsights.Web.Implementation.WebEventsSubscriber.OnEventWritten(EventWrittenEventArgs eventData)];