Comment 2 for bug 1200756

I have the same error, but all I did was add a button to a tree view
this is the code of the view:

<record id="lqp_purchase_order_pending_tree" model="ir.ui.view">
   <field name="name">lqp.purchase.order.pending.tree</field>
   <field name="model">sale.order.line</field>
   <field name="arch" type="xml">
    <tree string="Pendientes" editable="top">
     <field name="order_id" />
     <field name="product_id" />
     <field name="name" />
     <button string="Confirm" icon="gtk-redo" name="action_generate_purchase_order" type="object"/>
    </tree>
   </field>
        </record>