[FIX] website_event: Website Event Error when you encode a 0 value in the registration

The function registration_new must return a type json.

opw:765643

addons/website_event/controllers/main.py

@@ -253,7 +253,7 @@ class website_event(http.Controller):
     def registration_new(self, event, **post):
         tickets = self._process_tickets_details(post)
         if not tickets:
-            return request.redirect("/event/%s" % slug(event))
+            return False
         return request.website._render("website_event.registration_attendee_details", {'tickets': tickets, 'event': event})
 
     def _process_registration_details(self, details):