No fallback query for subsets for set
No fallback query for subsets for set

Query index greater than 0 indicates a fallback
query in the case that the initial one returned
no results. But in the case of subsets for set,
we have no fallback so just return null.

https://phabricator.endlessm.com/T12198

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib