fix error message

htdocs/langs/en_US/ticket.lang

@@ -228,6 +228,7 @@ TicketNotNotifyTiersAtCreate=Not notify company at create
 Unread=Unread
 TicketNotCreatedFromPublicInterface=Not available. Ticket was not created from public interface.
 PublicInterfaceNotEnabled=Public interface was not enabled
+ErrorTicketRefRequired=Ticket reference name is required
 
 #
 # Logs

htdocs/ticket/class/ticket.class.php

@@ -306,7 +306,7 @@ class Ticket extends CommonObject
         }
 
         if (empty($this->ref)) {
-            $this->errors[] = 'ErrorBadRef';
+            $this->errors[] = 'ErrorTicketRefRequired';
             dol_syslog(get_class($this) . "::create error -1 ref null", LOG_ERR);
             $result = -1;
         }