bugfix: $controls MUST not be NULL when calling ldap_search()

[utesche]

otherwise a TypeError Exception is raised:

TypeError thrown with message "ldap_search() expects parameter 9 to be array, null given"

Stacktrace: #10 TypeError in /.../Services/LDAP/classes/class.ilLDAPQuery.php:520 #9 ldap_search in /.../Services/LDAP/classes/class.ilLDAPQuery.php:520 #8 ilLDAPQuery:queryByScope in /.../Services/LDAP/classes/class.ilLDAPQuery.php:474 #7 ilLDAPQuery:readUserData in /.../Services/LDAP/classes/class.ilLDAPQuery.php:87 #6 ilLDAPQuery:fetchUser in /.../Services/LDAP/classes/class.ilAuthProviderLDAP.php:58