MediaWiki internal error.

Original exception: [ZgZbSTnrsbBZoXLshRcfFAAAApA] /data/Special:WhatLinksHere/Talk:Thunderfighter 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/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(203)
#0 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(273): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(191): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/title/Title.php(4006): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(1328): MediaWiki\Title\Title->getPageLanguage()
#5 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(651): SkinTemplate->buildContentNavigationUrlsInternal()
#6 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(188): SkinTemplate->getPortletsTemplateData()
#7 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinMustache.php(92): SkinTemplate->getTemplateData()
#8 /var/www/vhosts/buckwiki.com/httpdocs/w/skins/Citizen/includes/SkinCitizen.php(64): SkinMustache->getTemplateData()
#9 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinMustache.php(62): MediaWiki\Skins\Citizen\SkinCitizen->getTemplateData()
#10 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(181): SkinMustache->generateHTML()
#11 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/OutputPage.php(2899): SkinTemplate->outputPage()
#12 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/MediaWiki.php(941): OutputPage->output()
#13 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/MediaWiki.php(576): MediaWiki->main()
#14 /var/www/vhosts/buckwiki.com/httpdocs/w/index.php(50): MediaWiki->run()
#15 /var/www/vhosts/buckwiki.com/httpdocs/w/index.php(46): wfIndexMain()
#16 {main}

Exception caught inside exception handler: [ZgZbSTnrsbBZoXLshRcfFAAAApA] /data/Special:WhatLinksHere/Talk:Thunderfighter 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/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(203)
#0 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(273): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(191): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/title/Title.php(4006): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(1328): MediaWiki\Title\Title->getPageLanguage()
#5 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(651): SkinTemplate->buildContentNavigationUrlsInternal()
#6 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(188): SkinTemplate->getPortletsTemplateData()
#7 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinMustache.php(92): SkinTemplate->getTemplateData()
#8 /var/www/vhosts/buckwiki.com/httpdocs/w/skins/Citizen/includes/SkinCitizen.php(64): SkinMustache->getTemplateData()
#9 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinMustache.php(62): MediaWiki\Skins\Citizen\SkinCitizen->getTemplateData()
#10 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/skins/SkinTemplate.php(181): SkinMustache->generateHTML()
#11 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/OutputPage.php(2899): SkinTemplate->outputPage()
#12 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/exception/MWException.php(184): OutputPage->output()
#13 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/exception/MWException.php(218): MWException->reportHTML()
#14 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/exception/MWExceptionHandler.php(130): MWException->report()
#15 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/exception/MWExceptionHandler.php(249): MWExceptionHandler::report()
#16 /var/www/vhosts/buckwiki.com/httpdocs/w/includes/MediaWiki.php(595): MWExceptionHandler::handleException()
#17 /var/www/vhosts/buckwiki.com/httpdocs/w/index.php(50): MediaWiki->run()
#18 /var/www/vhosts/buckwiki.com/httpdocs/w/index.php(46): wfIndexMain()
#19 {main}