[trunk] AttributeError: 'pos_order' object has no attribute 'button_dummy'

Hello,

Test done on trunk:

(Build 1862)
server (4671)
addons (8274)
web (3587)

- Goto Point of Sales
- Orders
- Create new order
- Add products
- click on 'update' link to calcultate totals

Error popup appears:

Server Traceback (most recent call last):
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/addons/web/session.py", line 87, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/netsvc.py", line 281, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/service/web_services.py", line 603, in dispatch
    res = fn(db, uid, *params)
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/osv/osv.py", line 169, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/osv/osv.py", line 123, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/osv/osv.py", line 179, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/addons/audittrail/audittrail.py", line 514, in execute_cr
    return fct_src(cr, uid, model, method, *args, **kw)
  File "/home/odoo/runbot/static/openerp-dev-trunk-1862/server/openerp/osv/osv.py", line 166, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
AttributeError: 'pos_order' object has no attribute 'button_dummy'

The update of totals is however successful !

In a POS situation it is confusing and annoying...