When viewing the Flow changes of a user on Special:CheckUser, FlowHooks::onSpecialCheckUserGetLinksFromRow tries to format links but fails and spams the log with:
2017-01-06 16:03:45 mediawiki-vagrant wiki: FlowHooks::onSpecialCheckUserGetLinksFromRow: Exception formatting cu {"cuc_id":"8","cuc_namespace":"2600","cuc_title":"Tend0ijgozdoy5bf","cuc_user":"9","cuc_user_text":"Goodguy","cuc_actiontext":"","cuc_comment":"v1,reply,tend0ijgozdoy5bf,tend0ijldcomypgr","cuc_minor":"0","cuc_page_id":"0","cuc_this_oldid":"0","cuc_last_oldid":"0","cuc_type":"142","cuc_timestamp":"20161103132355","cuc_ip":"10.0.2.2","cuc_ip_hex":"0A000202","cuc_xff":"0","cuc_xff_hex":null,"cuc_agent":"Mozilla\/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/54.0.2840.71 Safari\/537.36","cuc_private":null} exception 'Flow\Exception\FlowException' with message 'could not locate workflow for revision tend0ijldcomypgr' in /vagrant/mediawiki/extensions/Flow/includes/Formatter/AbstractQuery.php:209