* mod_ldap: Correctly return all requested attribute values

when some attributes have a null value.

PR: 44560 
Submitted by: Anders Kaseorg <anders kaseorg.com>
Reviewed by: covener



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@634821 13f79535-47bb-0310-9956-ffa450edef68