Fix unhandled exception in LogError method.  Even though LogError was checking for null context, in application_start, the context is not null, but an exception was occurring when trying to access the Request property of the context (even though it's not null).  Updated Application_Start, and DrainTransactionQueue to pass a null context so that LogError wont try to access the Request property.  See: http://mvolo.com/iis7-integrated-mode-request-is-not-available-in-this-context-exception-in-applicationstart/