@Override
        public void remove() {
            delegate.remove();
            K key = current.getKey();
            V value = current.getValue();
            if (key instanceof String) {
                deleteProperty((String)key, value instanceof String ? (String)value : null);
            }
            current = null;
        }
Removes the property corresponding to the current key from
the underlying map. Also applies update to the database.
xmppserver/src/main/java/org/jivesoftware/openfire/group/DefaultGroupPropertyMap.java