[Mediawiki-l] Undefined variable: skin in .../includes/ChangesList.php on line 52.

[Webmaster Comunitatea Română]

I upgraded from MediaWiki 1.6.3 to 1.7.1. Everything went fine overall, I
didn't see any error and I can see the articles. 

When I try to see the history for an article, that's when I get this error
Undefined variable: skin in .../includes/ChangesList.php on line 52

Any ideas what's wrong?
Thanks,
Adrian