Cristal file system backend does not auto create html.json

In Electron when choosing File system backend and having nothing in $HOME/.cristal the following error occurs:

Error: Error invoking remote method 'readPage': Error: ENOENT: no such file or directory, open '/home/ludovic/.cristal/html.json'

(documentation in Release notes say you need to have .cristal, but it does not say anything of html.json and what should be in it by default). It's probably better if html.json and even .cristal are auto-created when missing.