In https://phabricator.miraheze.org/T1832#56064, @Samwilson wrote:

I'm getting a couple of errors (with latest master of Liberty):

Undefined index: notifications-alert in skins/Liberty/LibertyTemplate.php on line 638

Undefined index: notifications-message in /home/sam/code/wikimedia/mediawiki/skins/Liberty/LibertyTemplate.php on line 639

It seems to not be checking whether Echo is installed. I'd raise a bug with the developers, but their Phabricator is all in Korean.

에코 설치 여부 체크 안 하는 듯.