when DatabaseSettings are in an extension, index_treemenu.php doesn't load them.

The logs show the following error:
eZMySQLDB:
Connection error: Couldn't connect to database. Please try again later or inform the system administrator.
Access denied for user 'toto'@'localhost' (using password: NO)

Steps to reproduce

create an extension extension/test/
create a file in /extension/test/settings/site.ini.append.php with
[DatabaseSettings]
DatabaseImplementation=ezmysql
Server=localhost
User=user
Password=password
Database=database

remove the DatabaseSettings from settings/override/site.ini.append.php
activate the extension "test"