All query params that are empty now returns success
(http.StatusOK) instead of mixed http status codes
(http.StatusNoContent/http.StatusBadRequest/
http.StatusInternalServerError)
Closes: #2007
This is related to issue #3741 where fetching data from
invalid store, package panic.
Modify subspace.go to return errors instead of panic.
Also update other packages that import subspace and
handle errors.
Marin Basic