public void deletePrivacyList(String username, String listName) {
        // Trigger event that a privacy list is being deleted
        for (PrivacyListEventListener listener : listeners) {
            try {
                listener.privacyListDeleting(listName);
            } catch (Exception e) {
                logger.warn("An exception occurred while dispatching a 'privacyListDeleting' event!", e);
            }
        }
        // Remove the list from the cache
        listsCache.remove(getCacheKey(username, listName));
        // Delete the privacy list from the DB
        provider.deletePrivacyList(username, listName);
        // Check if deleted list was the default list
        PrivacyList defaultList = listsCache.get(getDefaultCacheKey(username));
        if (defaultList != null && listName.equals(defaultList.getName())) {
            listsCache.remove(getDefaultCacheKey(username));
        }
    }
Deletes an existing privacy list of a user. If the privacy list being deleted was
the default list then the user will end up with no default list. Therefore, the user
will have to set a new default list.

@param username the username of the list owner.
@param listName the name of the list being deleted.
xmppserver/src/main/java/org/jivesoftware/openfire/privacy/PrivacyListManager.java