MediaWiki internal error.

Original exception: [1d92c5d9f8b876006a4cdd09] /wiki/index.php/%ed%86%a0%eb%a1%a0:Endless_Planes/%ed%81%ac%eb%a1%9c%eb%85%b8%ec%8a%a4_%ed%96%89%ec%84%b1%ea%b3%84/%ed%81%ac%eb%a1%9c%eb%85%b8%ec%8a%a4 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/parser/ParserOptions.php(1444): MediaWiki\Title\Title->getPageLanguage()
#5 /var/www/html/wiki/includes/parser/ParserCache.php(293): ParserOptions->optionsHash()
#6 /var/www/html/wiki/includes/page/ParserOutputAccess.php(217): ParserCache->makeParserOutputKey()
#7 /var/www/html/wiki/includes/page/Article.php(650): MediaWiki\Page\ParserOutputAccess->getCachedParserOutput()
#8 /var/www/html/wiki/includes/page/Article.php(550): Article->generateContentOutput()
#9 /var/www/html/wiki/includes/actions/ViewAction.php(78): Article->view()
#10 /var/www/html/wiki/includes/MediaWiki.php(583): ViewAction->show()
#11 /var/www/html/wiki/includes/MediaWiki.php(363): MediaWiki->performAction()
#12 /var/www/html/wiki/includes/MediaWiki.php(960): MediaWiki->performRequest()
#13 /var/www/html/wiki/includes/MediaWiki.php(613): MediaWiki->main()
#14 /var/www/html/wiki/index.php(50): MediaWiki->run()
#15 /var/www/html/wiki/index.php(46): wfIndexMain()
#16 {main}

Exception caught inside exception handler: [1d92c5d9f8b876006a4cdd09] /wiki/index.php/%ed%86%a0%eb%a1%a0:Endless_Planes/%ed%81%ac%eb%a1%9c%eb%85%b8%ec%8a%a4_%ed%96%89%ec%84%b1%ea%b3%84/%ed%81%ac%eb%a1%9c%eb%85%b8%ec%8a%a4 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}