Low frequency but this is showing up in production logs:
Call to a member function hasInterwikiResults() on a non-object (null)
at: includes/specials/SpecialSearch.php:359
Stack:
#0 /srv/mediawiki/php-1.30.0-wmf.1/includes/specials/SpecialSearch.php(185): SpecialSearch->showResults(string)
#1 /srv/mediawiki/php-1.30.0-wmf.1/includes/specialpage/SpecialPage.php(522): SpecialSearch->execute(NULL)
#2 /srv/mediawiki/php-1.30.0-wmf.1/includes/specialpage/SpecialPageFactory.php(578): SpecialPage->run(NULL)
#3 /srv/mediawiki/php-1.30.0-wmf.1/includes/MediaWiki.php(287): SpecialPageFactory::executePath(Title, RequestContext)
#4 /srv/mediawiki/php-1.30.0-wmf.1/includes/MediaWiki.php(862): MediaWiki->performRequest()
#5 /srv/mediawiki/php-1.30.0-wmf.1/includes/MediaWiki.php(523): MediaWiki->main()
#6 /srv/mediawiki/php-1.30.0-wmf.1/index.php(43): MediaWiki->run()
#7 /srv/mediawiki/w/index.php(3): include(string)
#8 {main}