If no map class is passed in (should only happen on deserialization, and the real source map is provided on readObject), pass an empty immutable map to super, which is less weird and probably better than just ignoring and forcibly not calling the super constructor, which is what was happening.
If no map class is passed in (should only happen on deserialization, and the real source map is provided on readObject), pass an empty immutable map to super, which is less weird and probably better than just ignoring and forcibly not calling the super constructor, which is what was happening.

git-svn-id: a1a4b28b82a3276cc491891159dd9963a0a72fae@6105 542714f4-19e9-0310-aa3c-eee0fc999fb1

threerings/narya,threerings/narya,threerings/narya,threerings/narya,threerings/narya