Fatal error: OOUI\Exception: OOUI\Theme::singleton was called with no singleton theme set. in E:\xampp\htdocs\w\vendor\oojs\oojs-ui\php\Theme.php:31 Stack trace: #0 E:\xampp\htdocs\w\vendor\oojs\oojs-ui\php\Element.php(259): OOUI\Theme::singleton() #1 E:\xampp\htdocs\w\vendor\oojs\oojs-ui\php\Tag.php(507): OOUI\Element->toString() #2 E:\xampp\htdocs\w\extensions\VisualEditor\includes\Hooks.php(244): OOUI\Tag->__toString() #3 E:\xampp\htdocs\w\includes\HookContainer\HookContainer.php(161): MediaWiki\Extension\VisualEditor\Hooks->onTextSlotDiffRendererTablePrefix(Object(TextSlotDiffRenderer), Object(DerivativeContext), Array) #4 E:\xampp\htdocs\w\includes\HookContainer\HookRunner.php(1334): MediaWiki\HookContainer\HookContainer->run('TextSlotDiffRen...', Array) #5 E:\xampp\htdocs\w\includes\diff\TextSlotDiffRenderer.php(273): MediaWiki\HookContainer\HookRunner->onTextSlotDiffRendererTablePrefix(Object(TextSlotDiffRenderer), Object(DerivativeContext), Array) #6 E:\xampp\htdocs\w\includes\diff\DifferenceEngine.php(942): TextSlotDiffRenderer->getTablePrefix(Object(DerivativeContext), Object(MediaWiki\Title\Title)) #7 E:\xampp\htdocs\w\includes\diff\DifferenceEngine.php(928): DifferenceEngine->showTablePrefixes() #8 E:\xampp\htdocs\w\extensions\MobileFrontend\includes\specials\SpecialMobileDiff.php(189): DifferenceEngine->showDiffPage(true) #9 E:\xampp\htdocs\w\extensions\MobileFrontend\includes\specials\SpecialMobileDiff.php(143): SpecialMobileDiff->displayDiffPage() #10 E:\xampp\htdocs\w\extensions\MobileFrontend\includes\specials\MobileSpecialPage.php(71): SpecialMobileDiff->executeWhenAvailable('172') #11 E:\xampp\htdocs\w\includes\specialpage\SpecialPage.php(727): MobileSpecialPage->execute('172') #12 E:\xampp\htdocs\w\includes\specialpage\SpecialPageFactory.php(1621): MediaWiki\SpecialPage\SpecialPage->run('172') #13 E:\xampp\htdocs\w\includes\MediaWiki.php(357): MediaWiki\SpecialPage\SpecialPageFactory->executePath('\xE7\xA7\xBB\xE5\x8A\xA8\xE7\x89\x88\xE5\xB7\xAE\xE5\xBC\x82...', Object(RequestContext)) #14 E:\xampp\htdocs\w\includes\MediaWiki.php(960): MediaWiki->performRequest() #15 E:\xampp\htdocs\w\includes\MediaWiki.php(613): MediaWiki->main() #16 E:\xampp\htdocs\w\index.php(50): MediaWiki->run() #17 E:\xampp\htdocs\w\index.php(46): wfIndexMain() #18 {main} in E:\xampp\htdocs\w\vendor\oojs\oojs-ui\php\Tag.php on line 509