Fatal error: OOUI\Exception: OOUI\Theme::singleton was called with no singleton theme set. in C:\xampp\htdocs\Features\WIKI\vendor\oojs\oojs-ui\php\Theme.php:31 Stack trace: #0 C:\xampp\htdocs\Features\WIKI\vendor\oojs\oojs-ui\php\Element.php(259): OOUI\Theme::singleton() #1 C:\xampp\htdocs\Features\WIKI\vendor\oojs\oojs-ui\php\Tag.php(507): OOUI\Element->toString() #2 C:\xampp\htdocs\Features\WIKI\extensions\VisualEditor\includes\Hooks.php(244): OOUI\Tag->__toString() #3 C:\xampp\htdocs\Features\WIKI\includes\HookContainer\HookContainer.php(161): MediaWiki\Extension\VisualEditor\Hooks->onTextSlotDiffRendererTablePrefix(Object(TextSlotDiffRenderer), Object(RequestContext), Array) #4 C:\xampp\htdocs\Features\WIKI\includes\HookContainer\HookRunner.php(1334): MediaWiki\HookContainer\HookContainer->run('TextSlotDiffRen...', Array) #5 C:\xampp\htdocs\Features\WIKI\includes\diff\TextSlotDiffRenderer.php(273): MediaWiki\HookContainer\HookRunner->onTextSlotDiffRendererTablePrefix(Object(TextSlotDiffRenderer), Object(RequestContext), Array) #6 C:\xampp\htdocs\Features\WIKI\includes\diff\DifferenceEngine.php(942): TextSlotDiffRenderer->getTablePrefix(Object(RequestContext), Object(MediaWiki\Title\Title)) #7 C:\xampp\htdocs\Features\WIKI\includes\diff\DifferenceEngine.php(928): DifferenceEngine->showTablePrefixes() #8 C:\xampp\htdocs\Features\WIKI\includes\page\Article.php(979): DifferenceEngine->showDiffPage(false) #9 C:\xampp\htdocs\Features\WIKI\includes\page\Article.php(490): Article->showDiffPage() #10 C:\xampp\htdocs\Features\WIKI\includes\actions\ViewAction.php(78): Article->view() #11 C:\xampp\htdocs\Features\WIKI\includes\MediaWiki.php(583): ViewAction->show() #12 C:\xampp\htdocs\Features\WIKI\includes\MediaWiki.php(363): MediaWiki->performAction(Object(Article), Object(MediaWiki\Title\Title)) #13 C:\xampp\htdocs\Features\WIKI\includes\MediaWiki.php(960): MediaWiki->performRequest() #14 C:\xampp\htdocs\Features\WIKI\includes\MediaWiki.php(613): MediaWiki->main() #15 C:\xampp\htdocs\Features\WIKI\index.php(50): MediaWiki->run() #16 C:\xampp\htdocs\Features\WIKI\index.php(46): wfIndexMain() #17 {main} in C:\xampp\htdocs\Features\WIKI\vendor\oojs\oojs-ui\php\Tag.php on line 509