Fatal error: OOUI\Exception: OOUI\Theme::singleton was called with no singleton theme set. in /var/www/core/vendor/oojs/oojs-ui/php/Theme.php:31 Stack trace: #0 /var/www/core/vendor/oojs/oojs-ui/php/Element.php(259): OOUI\Theme::singleton() #1 /var/www/core/vendor/oojs/oojs-ui/php/Tag.php(507): OOUI\Element->toString() #2 /var/www/core/extensions/VisualEditor/includes/Hooks.php(244): OOUI\Tag->__toString() #3 /var/www/core/includes/HookContainer/HookContainer.php(161): MediaWiki\Extension\VisualEditor\Hooks->onTextSlotDiffRendererTablePrefix() #4 /var/www/core/includes/HookContainer/HookRunner.php(1334): MediaWiki\HookContainer\HookContainer->run() #5 /var/www/core/includes/diff/TextSlotDiffRenderer.php(273): MediaWiki\HookContainer\HookRunner->onTextSlotDiffRendererTablePrefix() #6 /var/www/core/includes/diff/DifferenceEngine.php(942): TextSlotDiffRenderer->getTablePrefix() #7 /var/www/core/includes/diff/DifferenceEngine.php(928): DifferenceEngine->showTablePrefixes() #8 /var/www/core/includes/page/Article.php(979): Diff in /var/www/core/vendor/oojs/oojs-ui/php/Tag.php on line 509