Fatal error: OOUI\Exception: OOUI\Theme::singleton was called with no singleton theme set. in /home/monaca/www/wiki/vendor/oojs/oojs-ui/php/Theme.php:31
Stack trace:
#0 /home/monaca/www/wiki/vendor/oojs/oojs-ui/php/Element.php(259): OOUI\Theme::singleton()
#1 /home/monaca/www/wiki/vendor/oojs/oojs-ui/php/Tag.php(510): OOUI\Element->toString()
#2 /home/monaca/www/wiki/extensions/VisualEditor/includes/Hooks.php(252): OOUI\Tag->__toString()
#3 /home/monaca/www/wiki/includes/HookContainer/HookContainer.php(159): MediaWiki\Extension\VisualEditor\Hooks->onTextSlotDiffRendererTablePrefix()
#4 /home/monaca/www/wiki/includes/HookContainer/HookRunner.php(1336): MediaWiki\HookContainer\HookContainer->run()
#5 /home/monaca/www/wiki/includes/diff/TextSlotDiffRenderer.php(278): MediaWiki\HookContainer\HookRunner->onTextSlotDiffRendererTablePrefix()
#6 /home/monaca/www/wiki/includes/diff/DifferenceEngine.php(1048): TextSlotDiffRenderer->getTablePrefix()
#7 /home/monaca/www/wiki/includes/diff/DifferenceEngine.php(1028): DifferenceEngine->showTablePrefixes()
#8 /home/monaca/www/wiki/includes/page/Article.php(1004): DifferenceEngine->showDiffPage()
#9 /home/monaca/www/wiki/includes/page/Article.php(503): Article->showDiffPage()
#10 /home/monaca/www/wiki/includes/actions/ViewAction.php(78): Article->view()
#11 /home/monaca/www/wiki/includes/actions/ActionEntryPoint.php(733): ViewAction->show()
#12 /home/monaca/www/wiki/includes/actions/ActionEntryPoint.php(510): MediaWiki\Actions\ActionEntryPoint->performAction()
#13 /home/monaca/www/wiki/includes/actions/ActionEntryPoint.php(145): MediaWiki\Actions\ActionEntryPoint->performRequest()
#14 /home/monaca/www/wiki/includes/MediaWikiEntryPoint.php(199): MediaWiki\Actions\ActionEntryPoint->execute()
#15 /home/monaca/www/wiki/index.php(58): MediaWiki\MediaWikiEntryPoint->run()
#16 {main} in /home/monaca/www/wiki/vendor/oojs/oojs-ui/php/Tag.php on line 512