Fix nullaway problems that appeared after reactor upgrade.

Signed-off-by: Gerrit Meier <meistermeier@gmail.com>

Author: meistermeier

src/main/java/org/springframework/data/neo4j/core/ReactiveNeo4jTemplate.java

@@ -566,7 +566,7 @@ private <T> Mono<Tuple2<T, DynamicLabels>> determineDynamicLabels(T entityToBeSa
 .one()
 .map(m -> (Collection<String>) m.get(Constants.NAME_OF_LABELS))
 .switchIfEmpty(Mono.just(Collections.emptyList()))
-.zipWith(Mono.just((Collection<String>) propertyAccessor.getProperty(p)))
+.zipWith(Mono.justOrEmpty((Collection<String>) propertyAccessor.getProperty(p)))
 .map(t -> Tuples.of(entityToBeSaved, new DynamicLabels(entityMetaData, t.getT1(), t.getT2())));
 }).orElse(Mono.just(Tuples.of(entityToBeSaved, DynamicLabels.EMPTY)));
 }

src/test/kotlin/org/springframework/data/neo4j/integration/reactive/ReactiveNeo4jClientKotlinInteropIT.kt

@@ -97,7 +97,7 @@ class ReactiveNeo4jClientKotlinInteropIT @Autowired constructor(
  }.one()
 
  StepVerifier.create(queen)
- .expectNextMatches { it.name == "Queen" && it.member.size == 4 }
+ .expectNextMatches { it!!.name == "Queen" && it.member.size == 4 }
  .verifyComplete()
 
  StepVerifier.create(neo4jClient.query("MATCH (n:IDontExists) RETURN id(n)").fetchAs<Long>().one())