On the Administration page (index.php?module=CoreAdminHome&action=home&idSite=1&period=week&date=today), I'm seeing four of these:

WARNING: /matomo/plugins/Live/Visualizations/VisitorLog.php(225): Notice - Trying to access array offset on value of type null - Matomo 3.13.1 - Please report this message in the Matomo forums: https://forum.matomo.org (please do a search first as it might have been reported already) (Module: Live, Action: getLastVisitsDetails, In CLI mode: false)

I'm seeing this after upgrading to 3.13.1 (PHP 7.4).

Originally posted by @c-prompt in #14701 (comment)