Handle ResponseEntity with null bodies [SPR-14663]

[spring-projects-issues]

Brian Clozel opened SPR-14663 and commented

Controller methods like the following throw NullPointerExceptions because the ResponseEntityResultHandler is trying to serialize the response entity body even though it's null:

@RequestMapping("/test")
public Mono<ResponseEntity<Void>> test() {
	return Mono.just(ResponseEntity.notFound().build());
}

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Affects: 5.0 M1

Reference URL: https://github.com/bclozel/spring-boot-web-reactive/issues/22

Referenced from: commits 01bd8b9