Allow empty arrays and hashes in structured facts

We were getting validation errors in factmap-to-paths code due to the lack
of proper handling for empty hashes and arrays. This patch drops those branches
quickly and now moves onto the next element.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #1021 from kbarber/maint/master/allow_empty_hashes_and_arrays_in_sfacts

Allow empty arrays and hashes in structured facts