Add a better message error on RoutingContextImpl #1119

Job	Run time
IT / GraphQLWS-Tests (18.13.0)	50s
IT / SockJS-WriteHandler-Tests (16.13.1)	1m 4s
CI (ubuntu-latest, 11) / Run tests	5m 44s
CI (windows-latest, 11) / Run tests	5m 41s
CI (ubuntu-latest, 21) / Run tests	5m 35s
Deploy	0s
	18m 54s

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