ApprovedRevs triggers an Error when:
- $egApprovedRevsBlankIfUnapproved = false AND
- a user opens an unapproved page.
In ApprovedRevsHooks::showBlankIfUnapproved( &$article, &$content ), instead of setting $content->mText = '' (which btw does not always exist, only if $content instanceof TextContent), $content should be set to a value of type WikitextContent. (I submit a patch in some minutes.)