unable to create invoice from sale order with latest revisions

hello,
I am on latest trunk revisions.
I am not able to create invoice after confirming the sale order. it gives me this....
I think the context is set to None instead of {} .
i have attached a patch too.

Traceback (most recent call last):
  File "/home/nch/openERP/latest/server/bin/netsvc.py", line 229, in dispatch
    result = LocalService(service_name)(method, *params)
  File "/home/nch/openERP/latest/server/bin/netsvc.py", line 74, in __call__
    return getattr(self, method)(*params)
  File "/home/nch/openERP/latest/server/bin/service/web_services.py", line 475, in exec_workflow
    res = service.exec_workflow(db, uid, object, method, id)
  File "/home/nch/openERP/latest/server/bin/osv/osv.py", line 59, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/nch/openERP/latest/server/bin/osv/osv.py", line 137, in exec_workflow
    res = self.exec_workflow_cr(cr, uid, obj, method, *args)
  File "/home/nch/openERP/latest/server/bin/osv/osv.py", line 130, in exec_workflow_cr
    return wf_service.trg_validate(uid, obj, args[0], method, cr)
  File "/home/nch/openERP/latest/server/bin/workflow/wkf_service.py", line 81, in trg_validate
    res2 = instance.validate(cr, id, ident, signal)
  File "/home/nch/openERP/latest/server/bin/workflow/instance.py", line 49, in validate
    workitem.process(cr, witem, ident, signal, force_running, stack=stack)
  File "/home/nch/openERP/latest/server/bin/workflow/workitem.py", line 62, in process
    ok = _split_test(cr, workitem, activity['split_mode'], ident, signal, stack)
  File "/home/nch/openERP/latest/server/bin/workflow/workitem.py", line 171, in _split_test
    _join_test(cr, t[0], t[1], ident, stack)
  File "/home/nch/openERP/latest/server/bin/workflow/workitem.py", line 179, in _join_test
    create(cr,[activity], inst_id, ident, stack)
  File "/home/nch/openERP/latest/server/bin/workflow/workitem.py", line 42, in create
    process(cr, res, ident, stack=stack)
  File "/home/nch/openERP/latest/server/bin/workflow/workitem.py", line 54, in process
    result = _execute(cr, workitem, activity, ident, stack)
  File "/home/nch/openERP/latest/server/bin/workflow/workitem.py", line 126, in _execute
    id_new = wkf_expr.execute(cr, ident, workitem, activity)
  File "/home/nch/openERP/latest/server/bin/workflow/wkf_expr.py", line 68, in execute
    return _eval_expr(cr, ident, workitem, activity['action'])
  File "/home/nch/openERP/latest/server/bin/workflow/wkf_expr.py", line 58, in _eval_expr
    ret = eval(line, env)
  File "<string>", line 0, in ?
  File "/home/nch/openERP/latest/server/bin/osv/orm.py", line 153, in <lambda>
    return lambda *args, **argv: getattr(self._table, name)(self._cr, self._uid, [self._id], *args, **argv)
  File "/home/nch/openERP/latest/addons/sale/sale.py", line 417, in action_invoice_create
    res = self._make_invoice(cr, uid, order, il)
  File "/home/nch/openERP/latest/addons/sale/sale.py", line 383, in _make_invoice
    inv_obj.button_compute(cr, uid, [inv_id])
  File "/home/nch/openERP/latest/addons/account/invoice.py", line 445, in button_compute
    self.button_reset_taxes(cr, uid, ids, context)
  File "/home/nch/openERP/latest/addons/account/invoice.py", line 436, in button_reset_taxes
    context.update({'lang': partner.lang})
AttributeError: 'NoneType' object has no attribute 'update'