Hi, I downloaded Hotel Management System for version 7, it is running, but when I want to create invoice, I have this error`

OpenERP Server Error

Client Traceback (most recent call last):
  File "/home/openerp/workspace/sankofa/openerp/addons/web/http.py", line 203, in dispatch
    response["result"] = method(self, **self.params)
  File "/home/openerp/workspace/sankofa/openerp/addons/web/controllers/main.py", line 1140, in exec_workflow
    return req.session.exec_workflow(model, id, signal)
  File "/home/openerp/workspace/sankofa/openerp/addons/web/session.py", line 148, in exec_workflow
    r = self.proxy('object').exec_workflow(self._db, self._uid, self._password, model, signal, id)
  File "/home/openerp/workspace/sankofa/openerp/addons/web/session.py", line 31, in proxy_method
    result = self.session.send(self.service_name, method, *args)
  File "/home/openerp/workspace/sankofa/openerp/addons/web/session.py", line 104, in send
    raise xmlrpclib.Fault(openerp.tools.ustr(e), formatted_info)


Server Traceback (most recent call last):
  File "/home/openerp/workspace/sankofa/openerp/addons/web/session.py", line 90, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/home/openerp/workspace/sankofa/openerp/netsvc.py", line 293, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/openerp/workspace/sankofa/openerp/service/web_services.py", line 626, in dispatch
    res = fn(db, uid, *params)
  File "/home/openerp/workspace/sankofa/openerp/osv/osv.py", line 131, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/openerp/workspace/sankofa/openerp/osv/osv.py", line 220, in exec_workflow
    res = self.exec_workflow_cr(cr, uid, obj, signal, *args)
  File "/home/openerp/workspace/sankofa/openerp/osv/osv.py", line 213, in exec_workflow_cr
    return object._workflow_signal(cr, uid, [res_id], signal)[res_id]
  File "/home/openerp/workspace/sankofa/openerp/osv/orm.py", line 3926, in _workflow_signal
    result[res_id] = wf_service.trg_validate(uid, self._name, res_id, signal, cr)
  File "/home/openerp/workspace/sankofa/openerp/workflow/wkf_service.py", line 119, in trg_validate
    res2 = instance.validate(cr, id, ident, signal)
  File "/home/openerp/workspace/sankofa/openerp/workflow/instance.py", line 43, in validate
    workitem.process(cr, witem, ident, signal, force_running, stack=stack)
  File "/home/openerp/workspace/sankofa/openerp/workflow/workitem.py", line 60, in process
    ok = _split_test(cr, workitem, activity['split_mode'], ident, signal, stack)
  File "/home/openerp/workspace/sankofa/openerp/workflow/workitem.py", line 175, in _split_test
    _join_test(cr, t[0], t[1], ident, stack)
  File "/home/openerp/workspace/sankofa/openerp/workflow/workitem.py", line 183, in _join_test
    create(cr,[activity], inst_id, ident, stack)
  File "/home/openerp/workspace/sankofa/openerp/workflow/workitem.py", line 40, in create
    process(cr, res, ident, stack=stack)
  File "/home/openerp/workspace/sankofa/openerp/workflow/workitem.py", line 52, in process
    result = _execute(cr, workitem, activity, ident, stack)
  File "/home/openerp/workspace/sankofa/openerp/workflow/workitem.py", line 127, in _execute
    id_new = wkf_expr.execute(cr, ident, workitem, activity)
  File "/home/openerp/workspace/sankofa/openerp/workflow/wkf_expr.py", line 67, in execute
    return _eval_expr(cr, ident, workitem, activity['action'])
  File "/home/openerp/workspace/sankofa/openerp/workflow/wkf_expr.py", line 57, in _eval_expr
    ret = eval(line, env, nocopy=True)
  File "/home/openerp/workspace/sankofa/openerp/tools/safe_eval.py", line 241, in safe_eval
    return eval(test_expr(expr, _SAFE_OPCODES, mode=mode), globals_dict, locals_dict)
  File "", line 1, in <module>
  File "/home/openerp/workspace/sankofa/openerp/osv/orm.py", line 374, in function_proxy
    return attr(self._cr, self._uid, [self._id], *args, **kwargs)
  File "/home/openerp/workspace/sankofa/sankofa_addons/hotel/hotel.py", line 214, in action_invoice_create
    invoice_id = self.pool.get('sale.order').action_invoice_create(cr, uid, ids, grouped=False, states=['confirmed', 'done'])
  File "/home/openerp/workspace/sankofa/openerp/addons/sale_stock/sale_stock.py", line 192, in action_invoice_create
    res = super(sale_order,self).action_invoice_create( cr, uid, ids, grouped=grouped, states=states, date_invoice = date_invoice, context=context)
  File "/home/openerp/workspace/sankofa/openerp/addons/sale/sale.py", line 540, in action_invoice_create
    res = self._make_invoice(cr, uid, order, il, context=context)
  File "/home/openerp/workspace/sankofa/openerp/addons/sale/sale.py", line 408, in _make_invoice
    inv_id = inv_obj.create(cr, uid, inv, context=context)
  File "/home/openerp/workspace/sankofa/openerp/addons/mail/mail_thread.py", line 242, in create
    thread_id = super(mail_thread, self).create(cr, uid, values, context=context)
  File "/home/openerp/workspace/sankofa/openerp/osv/orm.py", line 4478, in create
    self.pool.get(object)._store_set_values(cr, user, ids, fields2, context)
  File "/home/openerp/workspace/sankofa/openerp/osv/orm.py", line 4627, in _store_set_values
    result = self._columns[f].get(cr, self, ids, f, SUPERUSER_ID, context=context)
  File "/home/openerp/workspace/sankofa/openerp/osv/fields.py", line 1131, in get
    result = self._fnct(obj, cr, uid, ids, name, self._arg, context)
  File "/home/openerp/workspace/sankofa/openerp/osv/fields.py", line 1197, in _fnct_read
    value = value[field] or False
  File "/home/openerp/workspace/sankofa/openerp/osv/orm.py", line 383, in __getitem__
    raise KeyError(error_msg)
KeyError: "Field 'commercial_partner_id' does not exist in object 'browse_record(res.partner, 5)'"

`

help me to debug this error. Thanks