Internal error

From MicrobeWiki, the student-edited microbiology resource

[e7ec9970168f96218a4f5ca1] /index.php?title=Shigella&diff=next&oldid=5842 Error: Call to a member function getUser() on null

Backtrace:

from /var/lib/mediawiki/includes/diff/DifferenceEngine.php(1667)
#0 /var/lib/mediawiki/includes/diff/DifferenceEngine.php(1125): DifferenceEngine->getMultiNotice()
#1 /var/lib/mediawiki/includes/diff/DifferenceEngine.php(1080): DifferenceEngine->getDiff()
#2 /var/lib/mediawiki/includes/diff/DifferenceEngine.php(844): DifferenceEngine->showDiff()
#3 /var/lib/mediawiki/includes/page/Article.php(908): DifferenceEngine->showDiffPage()
#4 /var/lib/mediawiki/includes/page/Article.php(465): Article->showDiffPage()
#5 /var/lib/mediawiki/includes/actions/ViewAction.php(78): Article->view()
#6 /var/lib/mediawiki/includes/MediaWiki.php(542): ViewAction->show()
#7 /var/lib/mediawiki/includes/MediaWiki.php(322): MediaWiki->performAction()
#8 /var/lib/mediawiki/includes/MediaWiki.php(904): MediaWiki->performRequest()
#9 /var/lib/mediawiki/includes/MediaWiki.php(562): MediaWiki->main()
#10 /var/lib/mediawiki/index.php(50): MediaWiki->run()
#11 /var/lib/mediawiki/index.php(46): wfIndexMain()
#12 {main}