Fix a segfault in the LDAP cache purge.

PR:
Obtained from:
Submitted by:	Jess Holle <jessh ptc.com>
Reviewed by:


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@105206 13f79535-47bb-0310-9956-ffa450edef68