i did comment out the line in pi.js (110) and the images loads after a restart of the app, but after about 2 seconds the ui is refreshed and the image is gone again.
i checked <profilename>.json and inside the "states" tag the image property gets set to "0.png" when i add a button on a new profile and set a custom image.
But after that refresh i mentioned above that value looks like this and the default image is shown.