Update DB-Func.php

To fix the bug #5990 which in my opinion is a Blocker as it is not possible to save changes on a service template.

www/include/configuration/configObject/service/DB-Func.php

@@ -1181,7 +1181,7 @@ function updateService($service_id = null, $from_MC = false, $params = array())
     isset($ret["service_notifications_enabled"]["service_notifications_enabled"]) && $ret["service_notifications_enabled"]["service_notifications_enabled"] != 2 ? $rq .= "'".$ret["service_notifications_enabled"]["service_notifications_enabled"]."', " : $rq .= "'2', ";
 
     $rq .= "service_inherit_contacts_from_host = ";
-    isset($ret["service_inherit_contacts_from_host"]["service_inherit_contacts_from_host"]) && $ret["service_inherit_contacts_from_host"]["service_inherit_contacts_from_host"] != NULL ? $rq .= "'".$ret["service_inherit_contacts_from_host"]["service_inherit_contacts_from_host"]."', " : $rq .= "'NULL', ";
+    isset($ret["service_inherit_contacts_from_host"]["service_inherit_contacts_from_host"]) && $ret["service_inherit_contacts_from_host"]["service_inherit_contacts_from_host"] != NULL ? $rq .= "'".$ret["service_inherit_contacts_from_host"]["service_inherit_contacts_from_host"]."', " : $rq .= "NULL, ";
 
     $rq.= "contact_additive_inheritance = ";
     $rq .= (isset($ret['contact_additive_inheritance']) ? 1 : 0) . ', ';