=== Error ===
Request URL: Special:CheckUser + POST data
Request ID: `XS8wsgpAIC8AAF05UsoAAAAJ`
```name=message
Call to a member function userCan() on a non-object (null)
```
```name=trace,lines=10
#0 /srv/mediawiki/php-1.34.0-wmf.13/extensions/CheckUser/includes/specials/SpecialCheckUser.php(946): SpecialCheckUser->CUChangesLine(stdClass)
#1 /srv/mediawiki/php-1.34.0-wmf.13/extensions/CheckUser/includes/specials/SpecialCheckUser.php(745): SpecialCheckUser->doIPEditsRequestOutput(Wikimedia\Rdbms\ResultWrapper, string, boolean)
#2 /srv/mediawiki/php-1.34.0-wmf.13/extensions/CheckUser/includes/specials/SpecialCheckUser.php(110): SpecialCheckUser->doIPEditsRequest(string, boolean, integer)
#3 /srv/mediawiki/php-1.34.0-wmf.13/includes/specialpage/SpecialPage.php(571): SpecialCheckUser->execute(NULL)
#4 /srv/mediawiki/php-1.34.0-wmf.13/includes/specialpage/SpecialPageFactory.php(581): SpecialPage->run(NULL)
#5 /srv/mediawiki/php-1.34.0-wmf.13/includes/MediaWiki.php(288): MediaWiki\Special\SpecialPageFactory->executePath(Title, RequestContext)
#6 /srv/mediawiki/php-1.34.0-wmf.13/includes/MediaWiki.php(884): MediaWiki->performRequest()
#7 /srv/mediawiki/php-1.34.0-wmf.13/includes/MediaWiki.php(515): MediaWiki->main()
#8 /srv/mediawiki/php-1.34.0-wmf.13/index.php(42): MediaWiki->run()
#9 /srv/mediawiki/w/index.php(3): include(string)
#10 {main}
```
=== Impact ===
Reported by @Melos, seems to happen when requesting IP contributions on Special:CheckUser. I think it will completely prevent people from carrying out the CU.
Seen 21 times, starting with today. wmf.13 only.
=== Notes ===
-