Specify an empty string as a value.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@1382 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/skins/erp5_html_style/form_sort.pt

@@ -93,7 +93,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
             </select>
           </td>
           <td>
-            <span tal:replace="structure python:form.sort_order.render(request)" />
+            <span tal:replace="structure python:form.sort_order.render('', request)" />
           </td>
         </tr>
         </span>