Call to a member function isCurrent() on a non-object in /www/w/includes/Skin.php on line 1728
$wgArticle is not an object.
Reproducible at twn with input: title=Special:ComparePages&page1=User:purodha&page2=User:Siebrand&rev1=&rev2=
Version: 1.17.x
Severity: major