bugfix Cannot access offset of type string on string

kerioEmail_mx.php

@@ -186,11 +186,12 @@ function KerioEmailCheckDNS($params)
         'Debug MX',
         $clientDomains
     );
-
-    for($i=$clientDomains['startnumber'];$i<=$clientDomains['numreturned'];$i++) {
-        if($params['domain'] == $clientDomains['domains']['domain'][$i]['domainname']) {
-            $vars['selfDNS'] = TRUE;
-            $vars['domainId'] = $clientDomains['domains']['domain'][$i]['id'];
+    if(!empty($clientDomains['domains'])) {
+        for($i=$clientDomains['startnumber'];$i<=$clientDomains['numreturned'];$i++) {
+            if($params['domain'] == $clientDomains['domains']['domain'][$i]['domainname']) {
+                $vars['selfDNS'] = TRUE;
+                $vars['domainId'] = $clientDomains['domains']['domain'][$i]['id'];
+            }
         }
     }
     # SPF