Invalid special page name ""

Backtrace:

#0 /home/it/public_html/wiki/includes/Title.php(1893): SpecialPage::getTitleFor(NULL)
#1 /home/it/public_html/wiki/includes/Wiki.php(163): Title->userCanRead()
#2 /home/it/public_html/wiki/includes/Wiki.php(640): MediaWiki->performRequest()
#3 /home/it/public_html/wiki/includes/Wiki.php(547): MediaWiki->main()
#4 /home/it/public_html/wiki/index.php(57): MediaWiki->run()
#5 {main}