MediaWiki internal error.

Original exception: [b20c1aac0f94063cf4e5fc79] /wiki/index.php?title=%ED%86%A0%EB%A1%A0:%EC%A0%9C%EC%9D%B4%EC%9C%84%ED%82%A4&action=raw 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/page/WikiPage.php(251): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/wiki/includes/MediaWiki.php(480): WikiPage->getContentHandler()
#5 /var/www/html/wiki/includes/MediaWiki.php(361): MediaWiki->initializeArticle()
#6 /var/www/html/wiki/includes/MediaWiki.php(960): MediaWiki->performRequest()
#7 /var/www/html/wiki/includes/MediaWiki.php(613): MediaWiki->main()
#8 /var/www/html/wiki/index.php(50): MediaWiki->run()
#9 /var/www/html/wiki/index.php(46): wfIndexMain()
#10 {main}

Exception caught inside exception handler: [b20c1aac0f94063cf4e5fc79] /wiki/index.php?title=%ED%86%A0%EB%A1%A0:%EC%A0%9C%EC%9D%B4%EC%9C%84%ED%82%A4&action=raw 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/page/WikiPage.php(251): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/wiki/includes/page/WikiPage.php(237): WikiPage->getContentHandler()
#5 /var/www/html/wiki/includes/page/Article.php(2025): WikiPage->getActionOverrides()
#6 /var/www/html/wiki/includes/actions/ActionFactory.php(258): Article->getActionOverrides()
#7 /var/www/html/wiki/includes/actions/ActionFactory.php(405): MediaWiki\Actions\ActionFactory->getAction()
#8 /var/www/html/wiki/includes/context/RequestContext.php(306): MediaWiki\Actions\ActionFactory->getActionName()
#9 /var/www/html/wiki/includes/actions/Action.php(107): RequestContext->getActionName()
#10 /var/www/html/wiki/extensions/CodeMirror/includes/CodeMirrorHooks.php(24): Action::getActionName()
#11 /var/www/html/wiki/extensions/CodeMirror/includes/CodeMirrorHooks.php(38): CodeMirrorHooks::isCodeMirrorOnPage()
#12 /var/www/html/wiki/includes/HookContainer/HookContainer.php(161): CodeMirrorHooks::onBeforePageDisplay()
#13 /var/www/html/wiki/includes/HookContainer/HookRunner.php(941): MediaWiki\HookContainer\HookContainer->run()
#14 /var/www/html/wiki/includes/Output/OutputPage.php(2942): MediaWiki\HookContainer\HookRunner->onBeforePageDisplay()
#15 /var/www/html/wiki/includes/exception/MWExceptionRenderer.php(188): MediaWiki\Output\OutputPage->output()
#16 /var/www/html/wiki/includes/exception/MWExceptionRenderer.php(105): MWExceptionRenderer::reportHTML()
#17 /var/www/html/wiki/includes/exception/MWExceptionHandler.php(134): MWExceptionRenderer::output()
#18 /var/www/html/wiki/includes/exception/MWExceptionHandler.php(251): MWExceptionHandler::report()
#19 /var/www/html/wiki/includes/MediaWiki.php(632): MWExceptionHandler::handleException()
#20 /var/www/html/wiki/index.php(50): MediaWiki->run()
#21 /var/www/html/wiki/index.php(46): wfIndexMain()
#22 {main}