Don't crash if a page hasn't an endpoint

uitwww/cache.py

 # Source code of the Ubuntu-it website
-# Copyright (C) 2015  Pietro Albini <pietroalbini@ubuntu.com>
+# Copyright (C) 2015-2016  Pietro Albini <pietroalbini@ubuntu.com>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as published
@@ -45,6 +45,10 @@ def remove(path, recursive=False):
 
 def after_request(response):
     """Hook meant to be executed after a request"""
+    # Don't do anything if the page hasn't an endpoint
+    if flask.request.endpoint is None:
+        return response
+
     app = flask.current_app
 
     # Get the function for the current app