Error on configuration settings

Summary

The following error appears on the configuration of some Drupal sites

User warning: The following theme is missing from the file system: cern_components in drupal_get_filename() (line 276 of /drupal/8.6.13/core/includes/bootstrap.inc) #0 /drupal/8.6.13/core/includes/bootstrap.inc(584): _drupal_error_handler_real(512, 'The following t...', '/drupal/8.6.13/...', 276, Array) #1 [internal function]: _drupal_error_handler(512, 'The following t...', '/drupal/8.6.13/...', 276, Array) #2 /drupal/8.6.13/core/includes/bootstrap.inc(276): trigger_error('The following t...', 512) #3 /drupal/8.6.13/core/includes/bootstrap.inc(293): drupal_get_filename('theme', 'cern_components') #4 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php(394): drupal_get_path('theme', 'cern_components') #5 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php(85): Drupal\Core\Asset\LibraryDiscoveryParser->drupalGetPath('theme', 'cern_components') #6 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDiscoveryCollector.php(87): Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension('cern_components') #7 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDiscoveryCollector.php(66): Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions('cern_components') #8 /drupal/8.6.13/core/lib/Drupal/Core/Cache/CacheCollector.php(149): Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss('cern_components') #9 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDiscovery.php(44): Drupal\Core\Cache\CacheCollector->get('cern_components') #10 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDiscovery.php(58): Drupal\Core\Asset\LibraryDiscovery->getLibrariesByExtension('cern_components') #11 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDependencyResolver.php(54): Drupal\Core\Asset\LibraryDiscovery->getLibraryByName('cern_components', 'owlcarousel') #12 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDependencyResolver.php(56): Drupal\Core\Asset\LibraryDependencyResolver->doGetDependencies(Array, Array) #13 /drupal/8.6.13/core/lib/Drupal/Core/Asset/LibraryDependencyResolver.php(31): Drupal\Core\Asset\LibraryDependencyResolver->doGetDependencies(Array) #14 /drupal/8.6.13/core/lib/Drupal/Core/Asset/AssetResolver.php(104): Drupal\Core\Asset\LibraryDependencyResolver->getLibrariesWithDependencies(Array) #15 /drupal/8.6.13/core/lib/Drupal/Core/Asset/AssetResolver.php(116): Drupal\Core\Asset\AssetResolver->getLibrariesToLoad(Object(Drupal\Core\Asset\AttachedAssets)) #16 /drupal/8.6.13/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php(291): Drupal\Core\Asset\AssetResolver->getCssAssets(Object(Drupal\Core\Asset\AttachedAssets), false) #17 /drupal/8.6.13/core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php(161): Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAssetLibraries(Object(Drupal\Core\Asset\AttachedAssets), Array) #18 /drupal/8.6.13/core/lib/Drupal/Core/EventSubscriber/HtmlResponseSubscriber.php(45): Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAttachments(Object(Drupal\Core\Render\HtmlResponse)) #19 [internal function]: Drupal\Core\EventSubscriber\HtmlResponseSubscriber->onRespond(Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent), 'kernel.response', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher)) #20 /drupal/8.6.13/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(111): call_user_func(Array, Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent), 'kernel.response', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher)) #21 /drupal/8.6.13/vendor/symfony/http-kernel/HttpKernel.php(191): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.response', Object(Symfony\Component\HttpKernel\Event\FilterResponseEvent)) #22 /drupal/8.6.13/vendor/symfony/http-kernel/HttpKernel.php(173): Symfony\Component\HttpKernel\HttpKernel->filterResponse(Object(Drupal\Core\Render\HtmlResponse), Object(Symfony\Component\HttpFoundation\Request), 1) #23 /drupal/8.6.13/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) #24 /drupal/8.6.13/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #25 /drupal/8.6.13/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #26 /drupal/8.6.13/core/modules/page_cache/src/StackMiddleware/PageCache.php(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #27 /drupal/8.6.13/core/modules/page_cache/src/StackMiddleware/PageCache.php(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) #28 /drupal/8.6.13/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #29 /drupal/8.6.13/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #30 /drupal/8.6.13/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #31 /drupal/8.6.13/core/lib/Drupal/Core/DrupalKernel.php(693): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #32 /drupal/8.6.13/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) #33 {main}.