public bool TryFindByCode(ulong code, out DwarfAbbreviationItem item) failed

in DwarfAbbreviation.cs line 87;

   `public bool TryFindByCode(ulong code, out DwarfAbbreviationItem item)
    {
        item = null;
        if (code == 0)
        {
            return `false;
        }

        code--;

        if (_mapItems.Count > 0)
        {
            return _mapItems.TryGetValue(code, out item);
        }

        if (code < int.MaxValue && (int)code < _items.Count)
        {
            item = _items[(int) code];
            return true;
        }

        item = null;
        return false;
    }`

I found sometimes it failed at return _mapItems.TryGetValue(code, out item);
Then I fixed below; I do not konw if you have the same problem;

    `public` bool TryFindByCode(ulong code, out DwarfAbbreviationItem item)
    {
        item = null;
        if (code == 0)
        {
            return false;
        }

        //no need to minus 1
        //code--;

        if (_mapItems.Count > 0)
        {
            return _mapItems.TryGetValue(code, out item);
        }

        //if _mapItems is empty, try _items;
        if (code < int.MaxValue && (int)code <= _items.Count)
        {
            item = _items[(int) code - 1];
            return true;
        }

        item = null;
        return false;
    }

Start with DwarfAbbreviation.cs around line 87 and inspect TryFindByCode, including how the map and list are used. Reproduce the reported failure and determine which code-to-item indexing behavior is expected; done means the method consistently returns the correct item or false, with a regression test covering the failure.