MediaWiki internal error.

Original exception: [b74ef79630026671ffed7211] /wiki/User_talk:Skyyy.ari MWUnknownContentModelException: The content model 'flow-board' is not registered on this wiki.
See https://www.mediawiki.org/wiki/Content_handlers to find out which extensions handle this content model.
Backtrace:
from /var/www/litwiki/includes/content/ContentHandlerFactory.php(203)
#0 /var/www/litwiki/includes/content/ContentHandlerFactory.php(273): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/litwiki/includes/content/ContentHandlerFactory.php(191): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/litwiki/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/litwiki/includes/page/WikiPage.php(296): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/litwiki/includes/MediaWiki.php(437): WikiPage->getContentHandler()
#5 /var/www/litwiki/includes/MediaWiki.php(320): MediaWiki->initializeArticle()
#6 /var/www/litwiki/includes/MediaWiki.php(904): MediaWiki->performRequest()
#7 /var/www/litwiki/includes/MediaWiki.php(562): MediaWiki->main()
#8 /var/www/litwiki/index.php(50): MediaWiki->run()
#9 /var/www/litwiki/index.php(46): wfIndexMain()
#10 {main}

Exception caught inside exception handler: [b74ef79630026671ffed7211] /wiki/User_talk:Skyyy.ari MWUnknownContentModelException: The content model 'flow-board' is not registered on this wiki.
See https://www.mediawiki.org/wiki/Content_handlers to find out which extensions handle this content model.
Backtrace:
from /var/www/litwiki/includes/content/ContentHandlerFactory.php(203)
#0 /var/www/litwiki/includes/content/ContentHandlerFactory.php(273): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/litwiki/includes/content/ContentHandlerFactory.php(191): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/litwiki/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/litwiki/includes/page/WikiPage.php(296): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/litwiki/includes/page/WikiPage.php(282): WikiPage->getContentHandler()
#5 /var/www/litwiki/includes/page/Article.php(2071): WikiPage->getActionOverrides()
#6 /var/www/litwiki/includes/actions/ActionFactory.php(264): Article->getActionOverrides()
#7 /var/www/litwiki/includes/actions/ActionFactory.php(364): MediaWiki\Actions\ActionFactory->getAction()
#8 /var/www/litwiki/includes/context/RequestContext.php(305): MediaWiki\Actions\ActionFactory->getActionName()
#9 /var/www/litwiki/includes/skins/Skin.php(132): RequestContext->getActionName()
#10 /var/www/litwiki/includes/skins/SkinTemplate.php(228): Skin->getTemplateData()
#11 /var/www/litwiki/includes/skins/SkinMustache.php(88): SkinTemplate->getTemplateData()
#12 /var/www/litwiki/skins/Vector/includes/SkinVector.php(450): SkinMustache->getTemplateData()
#13 /var/www/litwiki/skins/Vector/includes/SkinVector22.php(168): MediaWiki\Skins\Vector\SkinVector->getTemplateData()
#14 /var/www/litwiki/includes/skins/SkinMustache.php(58): MediaWiki\Skins\Vector\SkinVector22->getTemplateData()
#15 /var/www/litwiki/includes/skins/SkinTemplate.php(177): SkinMustache->generateHTML()
#16 /var/www/litwiki/includes/OutputPage.php(2876): SkinTemplate->outputPage()
#17 /var/www/litwiki/includes/exception/MWException.php(181): OutputPage->output()
#18 /var/www/litwiki/includes/exception/MWException.php(215): MWException->reportHTML()
#19 /var/www/litwiki/includes/exception/MWExceptionHandler.php(129): MWException->report()
#20 /var/www/litwiki/includes/exception/MWExceptionHandler.php(248): MWExceptionHandler::report()
#21 /var/www/litwiki/includes/MediaWiki.php(581): MWExceptionHandler::handleException()
#22 /var/www/litwiki/index.php(50): MediaWiki->run()
#23 /var/www/litwiki/index.php(46): wfIndexMain()
#24 {main}