Occurs on https://m.mediawiki.org/wiki/User_talk:2001:16B8:1080:4E00:85A0:B72F:EC1:E270
Uncaught Error: Call to undefined method TitleValue::isSubpage() in /srv/mediawiki/php-1.36.0-wmf.4/skins/MinervaNeue/includes/Skins/SkinUserPageHelper.php:55 t exception.trace #0 /srv/mediawiki/php-1.36.0-wmf.4/skins/MinervaNeue/includes/Skins/SkinUserPageHelper.php(95): MediaWiki\Minerva\Skins\SkinUserPageHelper->fetchData() #1 /srv/mediawiki/php-1.36.0-wmf.4/skins/MinervaNeue/includes/ServiceWiring.php(105): MediaWiki\Minerva\Skins\SkinUserPageHelper->isUserPage() #2 /srv/mediawiki/php-1.36.0-wmf.4/vendor/wikimedia/services/src/ServiceContainer.php(447): Wikimedia\Services\ServiceContainer->{closure}(Object(MediaWiki\MediaWikiServices)) #3 /srv/mediawiki/php-1.36.0-wmf.4/vendor/wikimedia/services/src/ServiceContainer.php(416): Wikimedia\Services\ServiceContainer->createService('Minerva.Menu.Pa...') #4 /srv/mediawiki/php-1.36.0-wmf.4/skins/MinervaNeue/includes/Skins/SkinMinerva.php(169): Wikimedia\Services\ServiceContainer->getService('Minerva.Menu.Pa...') #5 /srv/mediawiki/php-1.36.0-wmf.4/skins/MinervaNeue/inc
My (unconfirmed) guess is this might have been caused by https://gerrit.wikimedia.org/r/c/mediawiki/skins/MinervaNeue/+/619118 cc @D3r1ck01