MediaWiki internal error.

Original exception: [ZfkICxkHRrIYOGNmE_DZkwAAAAE] /index.php?title=Special:UserLogin&returnto=Special%3AWhatLinksHere&returntoquery=target%3DHelp%253ANamespaces&mobileaction=toggle_view_mobile RuntimeException from line 60 of /home/somdwiki/public_html/extensions/MobileFrontend/includes/MobileFrontend.hooks.php: wgMFDefaultSkinClass is not setup correctly. It should point to the class name of a valid skin e.g. SkinMinerva, SkinVector
Backtrace:
#0 /home/somdwiki/public_html/extensions/MobileFrontend/includes/MobileFrontend.hooks.php(140): MobileFrontendHooks::getDefaultMobileSkin(RequestContext, MobileContext)
#1 /home/somdwiki/public_html/includes/Hooks.php(174): MobileFrontendHooks::onRequestContextCreateSkin(RequestContext, NULL)
#2 /home/somdwiki/public_html/includes/Hooks.php(202): Hooks::callHook(string, array, array, NULL)
#3 /home/somdwiki/public_html/includes/context/RequestContext.php(372): Hooks::run(string, array)
#4 /home/somdwiki/public_html/includes/specialpage/SpecialPage.php(746): RequestContext->getSkin()
#5 /home/somdwiki/public_html/includes/specialpage/LoginSignupSpecialPage.php(789): SpecialPage->getSkin()
#6 /home/somdwiki/public_html/includes/specialpage/LoginSignupSpecialPage.php(665): LoginSignupSpecialPage->getFakeTemplate(string, string)
#7 /home/somdwiki/public_html/includes/specialpage/AuthManagerSpecialPage.php(400): LoginSignupSpecialPage->getAuthForm(array, string)
#8 /home/somdwiki/public_html/includes/specialpage/LoginSignupSpecialPage.php(317): AuthManagerSpecialPage->trySubmit()
#9 /home/somdwiki/public_html/includes/specialpage/SpecialPage.php(569): LoginSignupSpecialPage->execute(NULL)
#10 /home/somdwiki/public_html/includes/specialpage/SpecialPageFactory.php(568): SpecialPage->run(NULL)
#11 /home/somdwiki/public_html/includes/MediaWiki.php(288): MediaWiki\Special\SpecialPageFactory->executePath(Title, RequestContext)
#12 /home/somdwiki/public_html/includes/MediaWiki.php(860): MediaWiki->performRequest()
#13 /home/somdwiki/public_html/includes/MediaWiki.php(517): MediaWiki->main()
#14 /home/somdwiki/public_html/index.php(42): MediaWiki->run()
#15 {main}

Exception caught inside exception handler: [ZfkICxkHRrIYOGNmE_DZkwAAAAE] /index.php?title=Special:UserLogin&returnto=Special%3AWhatLinksHere&returntoquery=target%3DHelp%253ANamespaces&mobileaction=toggle_view_mobile RuntimeException from line 60 of /home/somdwiki/public_html/extensions/MobileFrontend/includes/MobileFrontend.hooks.php: wgMFDefaultSkinClass is not setup correctly. It should point to the class name of a valid skin e.g. SkinMinerva, SkinVector
Backtrace:
#0 /home/somdwiki/public_html/extensions/MobileFrontend/includes/MobileFrontend.hooks.php(140): MobileFrontendHooks::getDefaultMobileSkin(RequestContext, MobileContext)
#1 /home/somdwiki/public_html/includes/Hooks.php(174): MobileFrontendHooks::onRequestContextCreateSkin(RequestContext, NULL)
#2 /home/somdwiki/public_html/includes/Hooks.php(202): Hooks::callHook(string, array, array, NULL)
#3 /home/somdwiki/public_html/includes/context/RequestContext.php(372): Hooks::run(string, array)
#4 /home/somdwiki/public_html/includes/context/ContextSource.php(137): RequestContext->getSkin()
#5 /home/somdwiki/public_html/includes/OutputPage.php(2670): ContextSource->getSkin()
#6 /home/somdwiki/public_html/includes/exception/MWExceptionRenderer.php(136): OutputPage->output()
#7 /home/somdwiki/public_html/includes/exception/MWExceptionRenderer.php(53): MWExceptionRenderer::reportHTML(RuntimeException)
#8 /home/somdwiki/public_html/includes/exception/MWExceptionHandler.php(98): MWExceptionRenderer::output(RuntimeException, integer)
#9 /home/somdwiki/public_html/includes/exception/MWExceptionHandler.php(172): MWExceptionHandler::report(RuntimeException)
#10 /home/somdwiki/public_html/includes/MediaWiki.php(544): MWExceptionHandler::handleException(RuntimeException)
#11 /home/somdwiki/public_html/index.php(42): MediaWiki->run()
#12 {main}