fetchExists is returning empty Mono instead of Mono containing false

[GeorgiPetkov]

When a query yields records then fetchExists behaves as expected (returns Mono containing true).
However, when there are no records fetchExists returns an empty Mono instead of Mono containing false.

In particular the code return fetchOne(existsQuery).map(Objects::nonNull) should be changed to return fetchOne(existsQuery).hasElement(). A Mono's element is never null so .map(Objects::nonNull) either does nothing (for empty Mono) or maps to true.

[gofabian]

Thanks for your report. We should fix this misbehaviour with your proposed change.