duplicate sale order NoneType ERROR - odoo

Question

when i duplicate a sale order, show this error:
AttributeError: 'NoneType' object has no attribute 'search'
before this action works fine, but I don't know why this problem appears now.
here the detail of the error:
Server Traceback (most recent call last):
File "/openerp/sitios/onak/odoo-7.0/addons/web/session.py", line 89, in send
return openerp.netsvc.dispatch_rpc(service_name, method, args)
File "/openerp/sitios/onak/odoo-7.0/openerp/netsvc.py", line 300, in dispatch_rpc
result = ExportService.getService(service_name).dispatch(method, params)
File "/openerp/sitios/onak/odoo-7.0/openerp/service/web_services.py", line 632, in dispatch
res = fn(db, uid, *params)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/osv.py", line 190, in execute_kw
return self.execute(db, uid, obj, method, *args, **kw or {})
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/osv.py", line 132, in wrapper
return f(self, dbname, *args, **kwargs)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/osv.py", line 199, in execute
res = self.execute_cr(cr, uid, obj, method, *args, **kw)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/osv.py", line 187, in execute_cr
return getattr(object, method)(cr, uid, *args, **kw)
File "/openerp/sitios/onak/odoo-7.0/addons/sale_stock/sale_stock.py", line 49, in copy
return super(sale_order, self).copy(cr, uid, id, default, context=context)
File "/openerp/community/addons/nuevo/sale_payment_method/sale.py", line 93, in copy
default, context=context)
File "/openerp/community/addons/nuevo/sale_exceptions/sale.py", line 262, in copy
cr, uid, id, default=default, context=context)
File "/openerp/sitios/onak/odoo-7.0/addons/sale/sale.py", line 80, in copy
return super(sale_order, self).copy(cr, uid, id, default, context=context)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/orm.py", line 5171, in copy
data = self.copy_data(cr, uid, id, default, context)
File "/openerp/community/addons/nuevo/magentoerpconnect/sale.py", line 163, in copy_data
context=context)
File "/openerp/sitios/onak/odoo-7.0/addons/mail/mail_thread.py", line 331, in copy_data
return super(mail_thread, self).copy_data(cr, uid, id, default=default, context=context)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/orm.py", line 5083, in copy_data
lines = [other.copy_data(cr, uid, line_id, context=context) for line_id in sorted(data[f])]
File "/openerp/community/addons/nuevo/magentoerpconnect/sale.py", line 301, in copy_data
context=context)
File "/openerp/sitios/onak/odoo-7.0/addons/sale/sale.py", line 868, in copy_data
return super(sale_order_line, self).copy_data(cr, uid, id, default, context=context)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/orm.py", line 5068, in copy_data
data = self.read(cr, uid, [id], fields_to_copy.keys(), context=context)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/orm.py", line 3707, in read
result = self._read_flat(cr, user, select, fields, context, load)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/orm.py", line 3830, in _read_flat
res2 = self._columns[f].get(cr, self, ids, f, user, context=context, values=res)
File "/openerp/sitios/onak/odoo-7.0/openerp/osv/fields.py", line 542, in get
ids2 = obj.pool.get(self._obj).search(cr, user, domain + [(self._fields_id, 'in', ids)], limit=self._limit, context=context)
AttributeError: 'NoneType' object has no attribute 'search'
somebody may help me please..
regards,