Error
MediaWiki version: 1.36.0-wmf.33
Argument 1 passed to MediaWiki\User\UserNameUtils::getCanonical() must be of the type string, null given, called in /srv/mediawiki/php-1.36.0-wmf.33/extensions/CentralAuth/includes/CentralAuthGroupMembershipProxy.php on line 48
Impact
Minor, for now.
Notes
Looks like a programming error to me. I admit any errors from authentication code makes me extra nervous.