MediaWiki internal error.

Original exception: [f132e689d85add3c2c7e3ad9] /wiki/Special:WhatLinksHere/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/Title.php(3943): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/litwiki/includes/skins/SkinTemplate.php(1521): Title->getPageLanguage()
#5 /var/www/litwiki/includes/skins/SkinTemplate.php(790): SkinTemplate->buildContentNavigationUrlsInternal()
#6 /var/www/litwiki/includes/skins/SkinTemplate.php(229): SkinTemplate->getPortletsTemplateData()
#7 /var/www/litwiki/includes/skins/SkinMustache.php(88): SkinTemplate->getTemplateData()
#8 /var/www/litwiki/skins/Vector/includes/SkinVector.php(450): SkinMustache->getTemplateData()
#9 /var/www/litwiki/skins/Vector/includes/SkinVector22.php(168): MediaWiki\Skins\Vector\SkinVector->getTemplateData()
#10 /var/www/litwiki/includes/skins/SkinMustache.php(58): MediaWiki\Skins\Vector\SkinVector22->getTemplateData()
#11 /var/www/litwiki/includes/skins/SkinTemplate.php(177): SkinMustache->generateHTML()
#12 /var/www/litwiki/includes/OutputPage.php(2876): SkinTemplate->outputPage()
#13 /var/www/litwiki/includes/MediaWiki.php(922): OutputPage->output()
#14 /var/www/litwiki/includes/MediaWiki.php(562): MediaWiki->main()
#15 /var/www/litwiki/index.php(50): MediaWiki->run()
#16 /var/www/litwiki/index.php(46): wfIndexMain()
#17 {main}

Exception caught inside exception handler: [f132e689d85add3c2c7e3ad9] /wiki/Special:WhatLinksHere/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/Title.php(3943): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/litwiki/includes/skins/SkinTemplate.php(1521): Title->getPageLanguage()
#5 /var/www/litwiki/includes/skins/SkinTemplate.php(790): SkinTemplate->buildContentNavigationUrlsInternal()
#6 /var/www/litwiki/includes/skins/SkinTemplate.php(229): SkinTemplate->getPortletsTemplateData()
#7 /var/www/litwiki/includes/skins/SkinMustache.php(88): SkinTemplate->getTemplateData()
#8 /var/www/litwiki/skins/Vector/includes/SkinVector.php(450): SkinMustache->getTemplateData()
#9 /var/www/litwiki/skins/Vector/includes/SkinVector22.php(168): MediaWiki\Skins\Vector\SkinVector->getTemplateData()
#10 /var/www/litwiki/includes/skins/SkinMustache.php(58): MediaWiki\Skins\Vector\SkinVector22->getTemplateData()
#11 /var/www/litwiki/includes/skins/SkinTemplate.php(177): SkinMustache->generateHTML()
#12 /var/www/litwiki/includes/OutputPage.php(2876): SkinTemplate->outputPage()
#13 /var/www/litwiki/includes/exception/MWException.php(181): OutputPage->output()
#14 /var/www/litwiki/includes/exception/MWException.php(215): MWException->reportHTML()
#15 /var/www/litwiki/includes/exception/MWExceptionHandler.php(129): MWException->report()
#16 /var/www/litwiki/includes/exception/MWExceptionHandler.php(248): MWExceptionHandler::report()
#17 /var/www/litwiki/includes/MediaWiki.php(581): MWExceptionHandler::handleException()
#18 /var/www/litwiki/index.php(50): MediaWiki->run()
#19 /var/www/litwiki/index.php(46): wfIndexMain()
#20 {main}