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(RequestContext), 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(RequestContext), Array) #6 E:\xampp\htdocs\w\includes\diff\DifferenceEngine.php(942): TextSlotDiffRenderer->getTablePrefix(Object(RequestContext), Object(MediaWiki\Title\Title)) #7 E:\xampp\htdocs\w\includes\diff\DifferenceEngine.php(928): DifferenceEngine->showTablePrefixes() #8 E:\xampp\htdocs\w\includes\page\Article.php(979): DifferenceEngine->showDiffPage(false) #9 E:\xampp\htdocs\w\includes\page\Article.php(490): Article->showDiffPage() #10 E:\xampp\htdocs\w\includes\page\ImagePage.php(156): Article->view() #11 E:\xampp\htdocs\w\includes\actions\ViewAction.php(78): ImagePage->view() #12 E:\xampp\htdocs\w\includes\MediaWiki.php(583): ViewAction->show() #13 E:\xampp\htdocs\w\includes\MediaWiki.php(363): MediaWiki->performAction(Object(ImagePage), Object(MediaWiki\Title\Title)) #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