This is the diff: https://meta.wikimedia.org/wiki/Special:AbuseFilter/history/71/diff/prev/600
This is the error:
PHP fatal error in /usr/local/apache/common-local/php-1.23wmf4/extensions/AbuseFilter/Views/AbuseFilterViewDiff.php line 30:
Call to undefined method TableDiffFormatterFullContext::_start_diff()
Version: master
Severity: major