[FIX] website_sale: user going to /shop/payment/validate/ without pass by mycart and add to cart

bzr revid: chm@openerp.com-20131203133345-0e7k3ab87u1d3we7

addons/website_sale/controllers/main.py

@@ -675,6 +675,8 @@ class Ecommerce(http.Controller):
 
         if transaction_id is None:
             tx = context.get('website_sale_transaction')
+            if not tx:
+                return request.redirect('/shop/')
         else:
             tx = request.registry['payment.transaction'].browse(cr, uid, transaction_id, context=context)