IntMap.mapValues crashes with a NPE

[aphyr]

Not totally sure what's up here, but map-value seems to work OK on normal maps, but not on int-maps. It looks like it passes a null value to the function?

(deftest ^:buggy map-values-test
  (let [m (i/from {1 10, 3 30})]
    (testing "IMap"
      ; This fails due to a bug I think
      (is (= {1 11 3 31} (datafy (m/map-values m (fn [k v]
                                                   (prn :k k :v v)
                                                   v))))))))

:k 0 :v nil
...
                          bifurcan-clj.int-map-test/fn                                                           int_map_test.clj:   77
                           bifurcan-clj.map/map-values                                                                    map.clj:  202
                   io.lacuna.bifurcan.IntMap.mapValues                                                                IntMap.java:   23
                   io.lacuna.bifurcan.IntMap.mapValues                                                                IntMap.java:  286
     io.lacuna.bifurcan.nodes.IntMapNodes$Node.mapVals                                                           IntMapNodes.java:  197
java.lang.NullPointerException: Cannot invoke "io.lacuna.bifurcan.nodes.IntMapNodes$Node.mapVals(Object, java.util.function.BiFunction)" because "<local3>.content[<local4>]" is null