Topic owners can remove a Docuss automatic category

[sylque]

When creating a topic from a Docuss page, categories are hidden from users. Indeed, categories are predefined by the webmaster (if using dcs-decorator.js) or the developer (if using dcs-html-based.js or comToPlugin.js). So far so good.
The issue is that, afterward, a topic owner can edit his topic and change/remove the categories (unless categories have been hidden everywhere using the docuss hide categories Discourse setting).