fix: if the max ordinal for a map value is zero then reserve 1 bit for it instead of nothing

[eduardoramirez]

Currently, when a Map is written where all the keys reference the same value ordinal and that ordinal is zero then we don't reserve any space for the value ordinal. when a map entry is hashed into the last bucket, it overflows when trying to set the value in the data array.

[Sunjeet]

Repro

    @Test
    public void triggerBugWithCurrentHashImpl() {
    ...    
        producer.runCycle((state) -> {
            for (int i=0; i<16384; i++) {  // exactly 16384 entries in the map, or a multiple thereof
                final long id = new Long(i);
                state.add(
                        new MapOfMovies(
                            new HashMap<Long, MyMovie>() {{
                                put(id, new MyMovie(0, "The Matrix")); // all entries pointing to same object at ordinal 0
                }}));
            }
        });
    }