authldap: avoid warning on invalid mapping setup. dokuwiki#4399

Author: splitbrain

lib/plugins/authldap/auth.php

@@ -253,7 +253,7 @@ protected function fetchUserData($user, $inbind = false)
                     // $key = array($key=>$regexp), only handles the first key-value
                     $regexp = current($key);
                     $key = key($key);
-                    if ($user_result[$key]) foreach ($user_result[$key] as $grpkey => $grp) {
+                    if (is_array($user_result[$key] ?? null)) foreach ($user_result[$key] as $grpkey => $grp) {
                         if ($grpkey !== 'count' && preg_match($regexp, $grp, $match)) {
                             if ($localkey == 'grps') {
                                 $info[$localkey][] = $match[1];