[ZflX3c9SAXAQufvXVqYLSAAAAAQ] /modlitewnik/ LogicException: Process cache for 'pl' should be set by now.

Backtrace:

from /usr/local/www/modlitewnik/includes/language/MessageCache.php(440)
#0 /usr/local/www/modlitewnik/includes/language/MessageCache.php(318): MessageCache->loadUnguarded(string, NULL)
#1 /usr/local/www/modlitewnik/includes/language/MessageCache.php(1162): MessageCache->load(string)
#2 /usr/local/www/modlitewnik/includes/language/MessageCache.php(1088): MessageCache->getMsgFromNamespace(string, string)
#3 /usr/local/www/modlitewnik/includes/language/MessageCache.php(1060): MessageCache->getMessageForLang(Language, string, boolean, array)
#4 /usr/local/www/modlitewnik/includes/language/MessageCache.php(999): MessageCache->getMessageFromFallbackChain(Language, string, boolean)
#5 /usr/local/www/modlitewnik/includes/language/Message.php(1473): MessageCache->get(string, boolean, Language)
#6 /usr/local/www/modlitewnik/includes/language/Message.php(970): Message->fetchMessage()
#7 /usr/local/www/modlitewnik/includes/language/Message.php(1053): Message->format(string)
#8 /usr/local/www/modlitewnik/includes/Title.php(715): Message->text()
#9 /usr/local/www/modlitewnik/includes/MediaWiki.php(142): Title::newMainPage()
#10 /usr/local/www/modlitewnik/includes/MediaWiki.php(162): MediaWiki->parseTitle()
#11 /usr/local/www/modlitewnik/includes/MediaWiki.php(860): MediaWiki->getTitle()
#12 /usr/local/www/modlitewnik/includes/MediaWiki.php(562): MediaWiki->main()
#13 /usr/local/www/modlitewnik/index.php(50): MediaWiki->run()
#14 /usr/local/www/modlitewnik/index.php(46): wfIndexMain()
#15 {main}