[turba] composed name while adding contact via link

[Martin]

    * Horde: 3.3.3
    * Imp: 4.3.3
    * Turba: H3 (2.3.1)


I cannot add contacts to my address book via the link in IMP's mail view. 
For example, the link URL contains

../message.php?..&actionID=add_address&name=FIRSTNAME+SURNAME&address=XXX.

So the field "name" is to be added as part of the contact. For my 
configuration, "name" is, however, a composition of several other fields. 
>From turba's sources.php:

'name' => array('fields' => array('namePrefix', 'firstname',
                                  'middlenames', 'lastname',
                                  'nameSuffix'),
                'format' => '%s %s %s %s %s',
                'parse' => array(
              array('fields' => array('firstname', 'middlenames',
                                      'lastname'),
                    'format' => '%s %s %s'),
              array('fields' => array('firstname', 'lastname'),
                    'format' => '%s %s')),
                'attribute' => 'cn'),


All I get is an empty "cn" field (and resulting from that an LDAP error). 
Is my sources.php misconfigured for the "name" field or is this a bug in 
toDriverKeys? I can add contacts via the "new contact" form of turba just 
fine.

Martin