MediaWiki internal error.

Original exception: [4269c4b0d63810d67b23ab2d] /index.php?title=Talk:ENGL_1101&mobileaction=toggle_view_mobile 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: [4269c4b0d63810d67b23ab2d] /index.php?title=Talk:ENGL_1101&mobileaction=toggle_view_mobile 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/skins/MinervaNeue/includes/Skins/SkinMinerva.php(921): RequestContext->getActionName()
#10 /var/www/litwiki/includes/OutputPage.php(2751): MediaWiki\Minerva\Skins\SkinMinerva->getDefaultModules()
#11 /var/www/litwiki/includes/OutputPage.php(2865): OutputPage->loadSkinModules()
#12 /var/www/litwiki/includes/exception/MWException.php(181): OutputPage->output()
#13 /var/www/litwiki/includes/exception/MWException.php(215): MWException->reportHTML()
#14 /var/www/litwiki/includes/exception/MWExceptionHandler.php(129): MWException->report()
#15 /var/www/litwiki/includes/exception/MWExceptionHandler.php(248): MWExceptionHandler::report()
#16 /var/www/litwiki/includes/MediaWiki.php(581): MWExceptionHandler::handleException()
#17 /var/www/litwiki/index.php(50): MediaWiki->run()
#18 /var/www/litwiki/index.php(46): wfIndexMain()
#19 {main}