reactor-core/src/main/java/reactor/core/publisher/Mono.java
public static <T> Mono<T> justOrEmpty(@Nullable T data) {
		return data != null ? just(data) : empty();
	}
public static <T> Mono<T> justOrEmpty(@Nullable T data) {
		return data != null ? just(data) : empty();
	}
Create a new {@link Mono} that emits the specified item if non null otherwise only emits
onComplete.

<p>
<img class="marble" src="doc-files/marbles/justOrEmpty.svg" alt="">
<p>
@param data the item to onNext or onComplete if null
@param <T> the type of the produced item

@return a {@link Mono}.