[imp] two sidebars with hordeauth => true enabled

[markus]

hi all,

I'm using the HEAD checkout's of horde imp and horde framework.

If I configure horde in the way that it the login takes place
automatically into imp with the hordeauth option in imp/config/servers.php

$servers['pop'] = array(
     'name' => 'POP3 Server',
     'server' => 'localhost',
     'hordeauth' => true,
...

But as soon I click on webmail I get a second sidebar.
A whole horde webmail website opens up in the existing one.

I'm sure there is an option to disable this.
But where !?

( if I use authentication throug imp in horde/config.php it
works fine. But I need the authentication done through the horde_users 
table)

thanks
Markus