lingo: protect "basket link cell" against anonymous ajax calls (#9045)

combo/apps/lingo/models.py

@@ -295,6 +295,8 @@ class LingoBasketLinkCell(CellBase):
         return len(items) > 0
 
     def render(self, context):
+        if not (getattr(context['request'], 'user', None) and context['request'].user.is_authenticated()):
+            return ''
         basket_template = template.loader.get_template('lingo/combo/basket_link.html')
         context['items'] = BasketItem.objects.filter(
                 user=context['request'].user, payment_date__isnull=True