[FIX] condition for displaying open/close arrow of tree views

failed to display it in the BOM structure screen even on nodes with children

lp bug: https://launchpad.net/bugs/877995 fixed

bzr revid: xmo@openerp.com-20111123142820-5o7wx3rqd5r18lgk

addons/web/static/src/xml/base.xml

@@ -534,16 +534,17 @@
         t-att-id="'treerow_' + record.id"
         t-att-data-id="record.id" t-att-data-level="level + 1">
     <t t-set="children" t-value="record[children_field]"/>
-    <t t-set="has_children" t-value="children and children.length"/>
+    <t t-set="class" t-value="children and children.length ? 'treeview-tr' : 'treeview-td'"/>
 
     <td t-foreach="fields_view" t-as="field"
         t-if="!field.attrs.modifiers.tree_invisible"
         t-att-data-id="record.id"
         t-att-style="color_for(record) + (!field_index ? 'background-position: ' + 19*level + 'px; padding-left: ' + 19*level + 'px;' : '')"
-        t-att-class="!field_index and has_children ? 'treeview-tr' : 'treeview-td'">
+        t-att-class="class">
         <span t-if="!field.attrs.modifiers.invisible">
             <t t-esc="render(record[field.attrs.name], fields[field.attrs.name])" />
         </span>
+        <t t-set="class" t-value="'treeview-td'"/>
     </td>
 </tr>