[FIX] traceback using write checks when user create

[Ariel E. Figueroa - http://www.humanytek.com]

Hi team, please see this issue .

http://youtu.be/UCSkfAh5U2c

Thanks!

[Ariel E. Figueroa - http://www.humanytek.com (arielfigue)]

Client Traceback (most recent call last):
  File "/home/openerp/server/openerp/addons/web/http.py", line 204, in dispatch
    response["result"] = method(self, **self.params)
  File "/home/openerp/server/openerp/addons/web/controllers/main.py", line 1128, in call_kw
    return self._call_kw(req, model, method, args, kwargs)
  File "/home/openerp/server/openerp/addons/web/controllers/main.py", line 1120, in _call_kw
    return getattr(req.session.model(model), method)(*args, **kwargs)
  File "/home/openerp/server/openerp/addons/web/session.py", line 42, in proxy
    result = self.proxy.execute_kw(self.session._db, self.session._uid, self.session._password, self.model, method, args, kw)
  File "/home/openerp/server/openerp/addons/web/session.py", line 30, in proxy_method
    result = self.session.send(self.service_name, method, *args)
  File "/home/openerp/server/openerp/addons/web/session.py", line 103, in send
    raise xmlrpclib.Fault(openerp.tools.ustr(e), formatted_info)

Server Traceback (most recent call last):
  File "/home/openerp/server/openerp/addons/web/session.py", line 89, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/home/openerp/server/openerp/netsvc.py", line 296, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/openerp/server/openerp/service/web_services.py", line 626, in dispatch
    res = fn(db, uid, *params)
  File "/home/openerp/server/openerp/osv/osv.py", line 190, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/home/openerp/server/openerp/osv/osv.py", line 132, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/openerp/server/openerp/osv/osv.py", line 199, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/openerp/server/openerp/osv/osv.py", line 187, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/openerp/server/openerp/addons/account_voucher_tax/account_voucher.py", line 70, in onchange_journal
    context=context)
  File "/home/openerp/server/openerp/addons/account_voucher_tax/account_voucher.py", line 427, in onchange_compute_tax
    lines_ids.extend(lines['value'].get('line_cr_ids'))
TypeError: 'NoneType' object is not iterable

[Ariel E. Figueroa - http://www.humanytek.com (arielfigue)]

done!