ComparisonOperators.Lte seems to match undefined/null value in switch caseOperator

ComparisonOperators.Lte seems to match undefined/null value in switch caseOperator

reactiveMongoTemplate.upsert(Query.query(
                                Criteria.where("id").is(b.getId())
                        ), AggregationUpdate.update()
                                .set("field.value").toValue(
                                        ConditionalOperators.switchCases(
                                                        CaseOperator.when(Gte.valueOf("field_priority")
                                                                        .greaterThanEqualToValue(b.getField().getPriority()))
                                                                .then("gte"),                                                
                                                        CaseOperator.when(Lte.valueOf("field_priority")
                                                                       .lessThanEqualToValue(b.getField().getPriority()))
                                                                .then("lt")
                                                )
                                                .defaultTo("default")
                                ), Bar.class)).flatMap(c -> Mono.just(foo));

if there is no document in the database we expect to run the default case, however we see the lte case is being ran.
We've tried fiddling with the order and gt, lt methods but none of them seem to accomplish what we're after.