Non-ASCII characters make TOC macro sad (BB-8875)

I'm using Creole's <<toc>> to list all pages on my wiki. When the macro detects a heading containing non-ASCII characters, like

= Sójka =

it stops processing the page, ignores the whole page in the TOC and spits out the error

Wiki macro error:

without giving any reason. Processing continues with the next page.

Removing the offensing character

= Sojka =

stops TOC macro whining and renders the page link correctly.

As I'm writing wiki pages in Polish, it is very common to have diacritics outside ASCII or Latin-1 in the headings.