Fatal error: OOUI\Exception: OOUI\Theme::singleton was called with no singleton theme set. in /var/www/html/vendor/oojs/oojs-ui/php/Theme.php:31
Stack trace:
#0 /var/www/html/vendor/oojs/oojs-ui/php/Element.php(259): OOUI\Theme::singleton()
#1 /var/www/html/vendor/oojs/oojs-ui/php/Tag.php(507): OOUI\Element->toString()
#2 /var/www/html/extensions/VisualEditor/includes/Hooks.php(244): OOUI\Tag->__toString()
#3 /var/www/html/includes/HookContainer/HookContainer.php(161): MediaWiki\Extension\VisualEditor\Hooks->onTextSlotDiffRendererTablePrefix(Object(TextSlotDiffRenderer), Object(DerivativeContext), Array)
#4 /var/www/html/includes/HookContainer/HookRunner.php(1334): MediaWiki\HookContainer\HookContainer->run('TextSlotDiffRen...', Array)
#5 /var/www/html/includes/diff/TextSlotDiffRenderer.php(273): MediaWiki\HookContainer\HookRunner->onTextSlotDiffRendererTablePrefix(Object(TextSlotDiffRenderer), Object(DerivativeContext), Array)
#6 /var/www/html/includes/diff/DifferenceEngine.php(942): TextSlotDiffRenderer->getTablePrefix(Object(DerivativeContext), Object(MediaWiki\Title\Title))
#7 /var/www/html/includes/diff/DifferenceEngine.php(928): DifferenceEngine->showTablePrefixes()
#8 /var/www/html/extensions/MobileFrontend/includes/specials/SpecialMobileDiff.php(189): DifferenceEngine->showDiffPage(true)
#9 /var/www/html/extensions/MobileFrontend/includes/specials/SpecialMobileDiff.php(143): SpecialMobileDiff->displayDiffPage()
#10 /var/www/html/extensions/MobileFrontend/includes/specials/MobileSpecialPage.php(71): SpecialMobileDiff->executeWhenAvailable('451')
#11 /var/www/html/includes/specialpage/SpecialPage.php(727): MobileSpecialPage->execute('451')
#12 /var/www/html/includes/specialpage/SpecialPageFactory.php(1621): MediaWiki\SpecialPage\SpecialPage->run('451')
#13 /var/www/html/includes/MediaWiki.php(357): MediaWiki\SpecialPage\SpecialPageFactory->executePath('MobileDiff/451', Object(RequestContext))
#14 /var/www/html/includes/MediaWiki.php(960): MediaWiki->performRequest()
#15 /var/www/html/includes/MediaWiki.php(613): MediaWiki->main()
#16 /var/www/html/index.php(50): MediaWiki->run()
#17 /var/www/html/index.php(46): wfIndexMain()
#18 {main} in /var/www/html/vendor/oojs/oojs-ui/php/Tag.php on line 509