MediaWiki internal error.

Original exception: [06f684558d8001b067922ddc] /wiki/index.php?title=%EC%82%AC%EC%9A%A9%EC%9E%90%ED%86%A0%EB%A1%A0:Ernst&action=info 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/html/wiki/includes/content/ContentHandlerFactory.php(192)
#0 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(247): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(181): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(93): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/html/wiki/includes/title/Title.php(3687): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/wiki/includes/actions/InfoAction.php(390): MediaWiki\Title\Title->getPageLanguage()
#5 /var/www/html/wiki/includes/actions/InfoAction.php(214): InfoAction->pageInfo()
#6 /var/www/html/wiki/includes/actions/FormlessAction.php(48): InfoAction->onView()
#7 /var/www/html/wiki/includes/MediaWiki.php(583): FormlessAction->show()
#8 /var/www/html/wiki/includes/MediaWiki.php(363): MediaWiki->performAction()
#9 /var/www/html/wiki/includes/MediaWiki.php(960): MediaWiki->performRequest()
#10 /var/www/html/wiki/includes/MediaWiki.php(613): MediaWiki->main()
#11 /var/www/html/wiki/index.php(50): MediaWiki->run()
#12 /var/www/html/wiki/index.php(46): wfIndexMain()
#13 {main}

Exception caught inside exception handler: [06f684558d8001b067922ddc] /wiki/index.php?title=%EC%82%AC%EC%9A%A9%EC%9E%90%ED%86%A0%EB%A1%A0:Ernst&action=info 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/html/wiki/includes/content/ContentHandlerFactory.php(192)
#0 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(247): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(181): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(93): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/html/wiki/includes/title/Title.php(3687): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/wiki/includes/skins/SkinTemplate.php(1299): MediaWiki\Title\Title->getPageLanguage()
#5 /var/www/html/wiki/includes/skins/SkinTemplate.php(604): SkinTemplate->buildContentNavigationUrlsInternal()
#6 /var/www/html/wiki/includes/skins/SkinTemplate.php(594): SkinTemplate->getPortletsTemplateData()
#7 /var/www/html/wiki/includes/skins/Skin.php(740): SkinTemplate->getCategoryLinks()
#8 /var/www/html/wiki/includes/skins/SkinTemplate.php(210): Skin->getCategories()
#9 /var/www/html/wiki/includes/skins/SkinTemplate.php(143): SkinTemplate->prepareQuickTemplate()
#10 /var/www/html/wiki/includes/skins/SkinTemplate.php(174): SkinTemplate->generateHTML()
#11 /var/www/html/wiki/includes/Output/OutputPage.php(2947): SkinTemplate->outputPage()
#12 /var/www/html/wiki/includes/exception/MWExceptionRenderer.php(188): MediaWiki\Output\OutputPage->output()
#13 /var/www/html/wiki/includes/exception/MWExceptionRenderer.php(105): MWExceptionRenderer::reportHTML()
#14 /var/www/html/wiki/includes/exception/MWExceptionHandler.php(134): MWExceptionRenderer::output()
#15 /var/www/html/wiki/includes/exception/MWExceptionHandler.php(251): MWExceptionHandler::report()
#16 /var/www/html/wiki/includes/MediaWiki.php(632): MWExceptionHandler::handleException()
#17 /var/www/html/wiki/index.php(50): MediaWiki->run()
#18 /var/www/html/wiki/index.php(46): wfIndexMain()
#19 {main}