MediaWiki internal error.

Original exception: [1d8cc97ed0fdb7f5c28b6d63] /wiki/%D9%86%D9%82%D8%A7%D8%B4_%D8%A7%D9%84%D8%AA%D8%B5%D9%86%D9%8A%D9%81:%D9%85%D8%B4%D8%B1%D9%88%D8%B9%D8%A7%D8%AA_%D8%A3%D8%B6%D9%81_%D8%AF%D8%B9%D9%85/edit?redlink=1 MWUnknownContentModelException from line 201 of /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php: 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:
#0 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php(266): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php(189): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/page/WikiPage.php(311): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/page/WikiPage.php(297): WikiPage->getContentHandler()
#5 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/page/Article.php(2547): WikiPage->getActionOverrides()
#6 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/actions/Action.php(130): Article->getActionOverrides()
#7 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/actions/Action.php(189): Action::factory()
#8 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/MediaWiki.php(166): Action::getActionName()
#9 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/MediaWiki.php(903): MediaWiki->getAction()
#10 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/MediaWiki.php(543): MediaWiki->main()
#11 /var/www/adef.xyz/wiki/mediawiki-1.35.1/index.php(53): MediaWiki->run()
#12 /var/www/adef.xyz/wiki/mediawiki-1.35.1/index.php(46): wfIndexMain()
#13 {main}

Exception caught inside exception handler: [1d8cc97ed0fdb7f5c28b6d63] /wiki/%D9%86%D9%82%D8%A7%D8%B4_%D8%A7%D9%84%D8%AA%D8%B5%D9%86%D9%8A%D9%81:%D9%85%D8%B4%D8%B1%D9%88%D8%B9%D8%A7%D8%AA_%D8%A3%D8%B6%D9%81_%D8%AF%D8%B9%D9%85/edit?redlink=1 MWUnknownContentModelException from line 201 of /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php: 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:
#0 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php(266): MediaWiki\Content\ContentHandlerFactory->validateContentHandler()
#1 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php(189): MediaWiki\Content\ContentHandlerFactory->createContentHandlerFromHook()
#2 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/content/ContentHandlerFactory.php(97): MediaWiki\Content\ContentHandlerFactory->createForModelID()
#3 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/page/WikiPage.php(311): MediaWiki\Content\ContentHandlerFactory->getContentHandler()
#4 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/page/WikiPage.php(297): WikiPage->getContentHandler()
#5 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/page/Article.php(2547): WikiPage->getActionOverrides()
#6 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/actions/Action.php(130): Article->getActionOverrides()
#7 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/actions/Action.php(189): Action::factory()
#8 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/skins/SkinTemplate.php(174): Action::getActionName()
#9 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/skins/SkinTemplate.php(373): SkinTemplate->wrapHTML()
#10 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/skins/SkinTemplate.php(127): SkinTemplate->prepareQuickTemplate()
#11 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/skins/SkinTemplate.php(144): SkinTemplate->generateHTML()
#12 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/OutputPage.php(2615): SkinTemplate->outputPage()
#13 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/exception/MWException.php(193): OutputPage->output()
#14 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/exception/MWException.php(231): MWException->reportHTML()
#15 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/exception/MWExceptionHandler.php(104): MWException->report()
#16 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/exception/MWExceptionHandler.php(185): MWExceptionHandler::report()
#17 /var/www/adef.xyz/wiki/mediawiki-1.35.1/includes/MediaWiki.php(576): MWExceptionHandler::handleException()
#18 /var/www/adef.xyz/wiki/mediawiki-1.35.1/index.php(53): MediaWiki->run()
#19 /var/www/adef.xyz/wiki/mediawiki-1.35.1/index.php(46): wfIndexMain()
#20 {main}