[O] org-wikinodes.el and "invalid format operation %%\"

[Michael Maurer]

I've enabled org-wikinodes.el to get CamelCase wiki links. But
whenever I try to follow a link/camelcase word, I just get "invalid
format operation %%\". Although there is a headline by that name in
the current file.
I'm using org-mode 9.1.6 and Emacs 25.3.1 64-bit on Win7.