Just tried an experiment in my test installation. Uninstalled DFWiki and NWiki. Installed NWiki. Still no continue button on wiki mod, but no blank files, either. Inserted a Wiki in a course. Edited a page. Edited a discussion. Everything worked.
Conclusion. There's some sort of conflict between NWiki and DFWiki, in my installations, anyway.
Problem. I have to convert some important work in DFWiki to NWiki, but to install NWiki properly, I seem to need to uninstall DFWiki. Can I convert under these circumstances?