The REST route /trackers/{id}/parent_artifacts, which is used to retrieve a list of suggested parents for an artifact of the given tracker, handles poorly cases where this list is empty. When the given tracker has no hierarchy and is not in a SAFe Program, when there are no "suggested parents" to return, it forgets to return any JSON. Worse, it also forgets to send pagination headers (X-PAGINATION-SIZE), which breaks our frontend client code handling paginated routes.
It should return an empty JSON array [] and headers with size = 0 when there are no "suggested parents".