Inconsistent .close() behavior for HTreeMap with .memoryDB() and .heapDB()

[puzpuzpuz]

The DB#close() method behaves in inconsistent manner in MapDB 3.0.7 behavior for HTreeMap with .memoryDB() and .heapDB().

Here is a simple reproducer:

DB db = DBMaker.memoryDB()
               .make();
HTreeMap<String, String> store = db.hashMap(TREE_NAME)
                                   .keySerializer(Serializer.STRING)
                                   .valueSerializer(Serializer.STRING)
                                   .create();
store.close();
// the next call throws java.lang.IllegalAccessError:
store.put("foo", "bar");

If you change .memoryDB() to .heapDB() the exception is not thrown (you can continue to call any operations on the store as if it's not closed). I'd expect the behavior to be the same, despite of the store type.