Fatal error: OOUI\Exception: OOUI\Theme::singleton was called with no singleton theme set. in /var/www/html/wiki/vendor/oojs/oojs-ui/php/Theme.php:31 Stack trace: #0 /var/www/html/wiki/vendor/oojs/oojs-ui/php/Element.php(259): OOUI\Theme::singleton() #1 /var/www/html/wiki/vendor/oojs/oojs-ui/php/Tag.php(510): OOUI\Element->toString() #2 /var/www/html/wiki/extensions/VisualEditor/includes/Hooks.php(252): OOUI\Tag->__toString() #3 /var/www/html/wiki/includes/HookContainer/HookContainer.php(159): MediaWiki\Extension\VisualEditor\Hooks->onTextSlotDiffRendererTablePrefix() #4 /var/www/html/wiki/includes/HookContainer/HookRunner.php(1338): MediaWiki\HookContainer\HookContainer->run() #5 /var/www/html/wiki/includes/diff/TextSlotDiffRenderer.php(278): MediaWiki\HookContainer\HookRunner->onTextSlotDiffRendererTablePrefix() #6 /var/www/html/wiki/includes/diff/DifferenceEngine.php(1048): TextSlotDiffRenderer->getTablePrefix() #7 /var/www/html/wiki/includes/diff/DifferenceEngine.php(1028): DifferenceEngine->showTablePrefixes() #8 /var/www/html/wiki/includes/page/Article.php(1004): DifferenceEngine->showDiffPage() #9 /var/www/html/wiki/includes/page/Article.php(503): Article->showDiffPage() #10 /var/www/html/wiki/includes/page/CategoryPage.php(63): Article->view() #11 /var/www/html/wiki/includes/actions/ViewAction.php(78): CategoryPage->view() #12 /var/www/html/wiki/includes/actions/ActionEntryPoint.php(733): ViewAction->show() #13 /var/www/html/wiki/includes/actions/ActionEntryPoint.php(510): MediaWiki\Actions\ActionEntryPoint->performAction() #14 /var/www/html/wiki/includes/actions/ActionEntryPoint.php(145): MediaWiki\Actions\ActionEntryPoint->performRequest() #15 /var/www/html/wiki/includes/MediaWikiEntryPoint.php(199): MediaWiki\Actions\ActionEntryPoint->execute() #16 /var/www/html/wiki/index.php(58): MediaWiki\MediaWikiEntryPoint->run() #17 {main} in /var/www/html/wiki/vendor/oojs/oojs-ui/php/Tag.php on line 512