MediaWiki internal error.

Original exception: [e74ee6b233cc21f73bf86373] /index.php?title=%D0%9E%D0%B1%D1%81%D1%83%D0%B6%D0%B4%D0%B5%D0%BD%D0%B8%D0%B5_%D1%83%D1%87%D0%B0%D1%81%D1%82%D0%BD%D0%B8%D0%BA%D0%B0:%D0%A2%D0%B5%D1%81%D1%82&action=edit&redlink=1 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/includes/content/ContentHandlerFactory.php(203)
#0 /var/www/html/includes/content/ContentHandlerFactory.php(272): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/html/includes/content/ContentHandlerFactory.php(191): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/html/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/html/includes/MediaWiki.php(435): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/includes/MediaWiki.php(319): MediaWiki->initializeArticle()
#5 /var/www/html/includes/MediaWiki.php(912): MediaWiki->performRequest()
#6 /var/www/html/includes/MediaWiki.php(563): MediaWiki->main()
#7 /var/www/html/index.php(53): MediaWiki->run()
#8 /var/www/html/index.php(46): wfIndexMain()
#9 {main}

Exception caught inside exception handler: [e74ee6b233cc21f73bf86373] /index.php?title=%D0%9E%D0%B1%D1%81%D1%83%D0%B6%D0%B4%D0%B5%D0%BD%D0%B8%D0%B5_%D1%83%D1%87%D0%B0%D1%81%D1%82%D0%BD%D0%B8%D0%BA%D0%B0:%D0%A2%D0%B5%D1%81%D1%82&action=edit&redlink=1 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/includes/content/ContentHandlerFactory.php(203)
#0 /var/www/html/includes/content/ContentHandlerFactory.php(272): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/html/includes/content/ContentHandlerFactory.php(191): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/html/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/html/includes/page/WikiPage.php(300): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/html/includes/page/WikiPage.php(286): WikiPage->getContentHandler()
#5 /var/www/html/includes/page/Article.php(2039): WikiPage->getActionOverrides()
#6 /var/www/html/includes/actions/ActionFactory.php(262): Article->getActionOverrides()
#7 /var/www/html/includes/actions/ActionFactory.php(361): MediaWiki\Actions\ActionFactory->getAction()
#8 /var/www/html/includes/actions/Action.php(111): MediaWiki\Actions\ActionFactory->getActionName()
#9 /var/www/html/extensions/DiscussionTools/includes/Hooks/HookUtils.php(228): Action::getActionName()
#10 /var/www/html/extensions/DiscussionTools/includes/Hooks/PageHooks.php(89): MediaWiki\Extension\DiscussionTools\Hooks\HookUtils::isFeatureEnabledForOutput()
#11 /var/www/html/includes/HookContainer/HookContainer.php(160): MediaWiki\Extension\DiscussionTools\Hooks\PageHooks->onBeforePageDisplay()
#12 /var/www/html/includes/HookContainer/HookRunner.php(936): MediaWiki\HookContainer\HookContainer->run()
#13 /var/www/html/includes/OutputPage.php(2802): MediaWiki\HookContainer\HookRunner->onBeforePageDisplay()
#14 /var/www/html/includes/exception/MWException.php(187): OutputPage->output()
#15 /var/www/html/includes/exception/MWException.php(221): MWException->reportHTML()
#16 /var/www/html/includes/exception/MWExceptionHandler.php(105): MWException->report()
#17 /var/www/html/includes/exception/MWExceptionHandler.php(202): MWExceptionHandler::report()
#18 /var/www/html/includes/MediaWiki.php(582): MWExceptionHandler::handleException()
#19 /var/www/html/index.php(53): MediaWiki->run()
#20 /var/www/html/index.php(46): wfIndexMain()
#21 {main}