These would manifest in the HTTP output as Javascript nulls instead of
empty lists, so we had unintentionally changed the interface while
porting to the new state store. We added code to each HTTP endpoint to
convert nil slices to empty ones so they JSON-ify properly, and we added
tests to catch this in the future.
Two of the changes are in tests; the one of consequence is in the API.
As explained in #1308 this can cause conflicts with downstream programs.
Fixes#1308.
James Phillips