Ticket 50428 - Log the actual base DN when the search fails with "invalid attribute request"
    
    Bug Description:
    When a search fails because it requests more than one empty attribute,
    the search base DN is always logged as "(null)".
    
    Fix Description:
    The search base DN for the failed search request is logged.
    This commit includes the automated test to verify the correct behavior.
    
    Fixes https://pagure.io/389-ds-base/issue/50428
    Relates: https://pagure.io/389-ds-base/issue/49969
    
    Author: Sylvie Gouverneyre
    
    Reviewed by: Viktor Ashirov, Simon Pichugin, Thierry Bordaz