Avatar caching does not work properly

[RandomTannenbaum]

When creating or editing a person you can upload an avatar. When the form validation fails the avatar should be loaded from cache. At the moment it seems like the path to the cache is broken or something, since the application is not able to load the cached avatar after a failed form validation. This looks like this:

ToDo

• [ ] Make the application load the image from cache correctly, so it is still shown after a form validation has failed