I've somehow managed to remove the toolbar and menu-bar from Okular. And after I found no way to reactivate them from "outside" – sice I can't click on Options anymore. I tried to reinstall a clean version after removing it with `apt-get remove --purge okular`, but it didn't work but it remained the same. I also looked for any configuration files in the home directory, without success. How should I proceed now in order to restore a clean Okular.