Add HTTP 404 error on non-existent note downloads

When FreeURL mode is enabled and you called the /download route, the note was created and the user redirected to the blank note.
This is caused because the findNote method automatically creates a note when no existing one is found.
This commit adds a new parameter to the findNote method which allows to disable this behaviour. In that case a HTTP 404 error will be returned.

Signed-off-by: Erik Michelson <github@erik.michelson.eu>

lib/web/note/controller.js

@@ -119,7 +119,7 @@ exports.doAction = function (req, res, next) {
       default:
         return res.redirect(config.serverURL + '/' + noteId)
     }
-  })
+  }, null, false)
 }
 
 exports.downloadMarkdown = function (req, res, note) {