HPCC-11278 Fix core when calling WUListQueriesUsingFile with LDAP

Signed-off-by: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
Merge pull request #5757 from afishbeck/fileUsedByQueriesLdapCore

HPCC-11278 Fix core when calling WUListQueriesUsingFile with LDAP

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>