MediaWiki internal error.

Original exception: [07f72563f10a88d94d0b83ee] /wiki/index.php/%ec%82%ac%ec%9a%a9%ec%9e%90%ed%86%a0%eb%a1%a0:Ernst 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(201)
#0 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(270): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(189): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/html/wiki/includes/MediaWiki.php(430): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/wiki/includes/MediaWiki.php(313): MediaWiki->initializeArticle()
#5 /var/www/html/wiki/includes/MediaWiki.php(918): MediaWiki->performRequest()
#6 /var/www/html/wiki/includes/MediaWiki.php(551): MediaWiki->main()
#7 /var/www/html/wiki/index.php(53): MediaWiki->run()
#8 /var/www/html/wiki/index.php(46): wfIndexMain()
#9 {main}

Exception caught inside exception handler: [07f72563f10a88d94d0b83ee] /wiki/index.php/%ec%82%ac%ec%9a%a9%ec%9e%90%ed%86%a0%eb%a1%a0:Ernst 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(201)
#0 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(270): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(189): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/html/wiki/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/html/wiki/includes/Title.php(4461): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/wiki/includes/skins/SkinTemplate.php(178): Title->getPageViewLanguage()
#5 /var/www/html/wiki/includes/skins/SkinTemplate.php(373): SkinTemplate->wrapHTML()
#6 /var/www/html/wiki/includes/skins/SkinTemplate.php(129): SkinTemplate->prepareQuickTemplate()
#7 /var/www/html/wiki/includes/skins/SkinTemplate.php(146): SkinTemplate->generateHTML()
#8 /var/www/html/wiki/includes/OutputPage.php(2634): SkinTemplate->outputPage()
#9 /var/www/html/wiki/includes/exception/MWException.php(193): OutputPage->output()
#10 /var/www/html/wiki/includes/exception/MWException.php(231): MWException->reportHTML()
#11 /var/www/html/wiki/includes/exception/MWExceptionHandler.php(104): MWException->report()
#12 /var/www/html/wiki/includes/exception/MWExceptionHandler.php(185): MWExceptionHandler::report()
#13 /var/www/html/wiki/includes/MediaWiki.php(570): MWExceptionHandler::handleException()
#14 /var/www/html/wiki/index.php(53): MediaWiki->run()
#15 /var/www/html/wiki/index.php(46): wfIndexMain()
#16 {main}