Error
MediaWiki version: n/a
https://logstash.wikimedia.org/app/kibana#/doc/logstash-*/logstash-2020.09.03/clienterror/?id=AXRTkqhEMQ_08tQafzOd
message
Uncaught TypeError: Cannot read property 'metaKey' of undefined
The same code path also triggers " TypeError: event is undefined".