Notice: Undefined index: data-user-name in /var/www/html/w/extensions/MobileFrontend/includes/skins/MinervaTemplate.php on line 200
Revision::getUser() can return 0 (e.g. the user doesn't have the right to see the username or the user is anonymous), which will be interpreted as false in php and we only add data-user-gender in:
https://github.com/wikimedia/mediawiki-extensions-MobileFrontend/blob/master/includes/skins/SkinMinerva.php#L641-L654