@Jdforrester-WMF reported this on IRC. From exception.log on fluorine.
It happened on a Flow topic, but doesn't seem it's actually caused by Flow.
2016-03-08 23:48:28 mw1150 mediawikiwiki 1.27.0-wmf.16 exception ERROR: [ed990e45] /wiki/Topic:Sztl7fb1akhaoido BadMethodCallException from line 740 of /srv/mediawiki/php-1.27.0-wmf.16/extensions/Echo/Hooks.php: Call to a member function getEventType() on a non-object (array) {"exception_id":"ed990e45"}
[Exception BadMethodCallException] (/srv/mediawiki/php-1.27.0-wmf.16/extensions/Echo/Hooks.php:740) Call to a member function getEventType() on a non-object (array)
#0 /srv/mediawiki/php-1.27.0-wmf.16/includes/Hooks.php(195): EchoHooks::onPersonalUrls(array, Title, SkinVector)
#1 /srv/mediawiki/php-1.27.0-wmf.16/includes/skins/SkinTemplate.php(693): Hooks::run(string, array)
#2 /srv/mediawiki/php-1.27.0-wmf.16/includes/skins/SkinTemplate.php(453): SkinTemplate->buildPersonalUrls()
#3 /srv/mediawiki/php-1.27.0-wmf.16/includes/skins/SkinTemplate.php(238): SkinTemplate->prepareQuickTemplate()
#4 /srv/mediawiki/php-1.27.0-wmf.16/includes/OutputPage.php(2363): SkinTemplate->outputPage()
#5 /srv/mediawiki/php-1.27.0-wmf.16/includes/MediaWiki.php(746): OutputPage->output()
#6 /srv/mediawiki/php-1.27.0-wmf.16/includes/MediaWiki.php(519): MediaWiki->main()
#7 /srv/mediawiki/php-1.27.0-wmf.16/index.php(43): MediaWiki->run()
#8 /srv/mediawiki/w/index.php(3): include(string)
#9 {main}