pull on empty collection of refs throws exception

[stevebuik]

(let [db1 (->> {:id   "10"
                :name "Enzo"
                :cars  [] }
               (vector :dx/merge)
               (dx/commit (dx/create-dx)))]
  (dx/pull db1 [:name {:cars [:id :name]}] [:id "10"]))

throws No such element exception

[stevebuik]

fix confirmed in Hotplate