Site Failure

My Drupal 8 site is giving me the following error message. Any help appreciated.

The website encountered an unexpected error. Please try again later.
Error: Cannot use assign-op operators with overloaded objects nor string offsets in DrupalCoreAssetLibraryDiscoveryParser->buildByExtension() (line 138 of core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php).
DrupalCoreAssetLibraryDiscoveryParser->buildByExtension(‘tweet’) (Line: 87)
DrupalCoreAssetLibraryDiscoveryCollector->getLibraryDefinitions(‘tweet’) (Line: 66)
DrupalCoreAssetLibraryDiscoveryCollector->resolveCacheMiss(‘tweet’) (Line: 148)
DrupalCoreCacheCacheCollector->get(‘tweet’) (Line: 44)
DrupalCoreAssetLibraryDiscovery->getLibrariesByExtension(‘tweet’) (Line: 58)
DrupalCoreAssetLibraryDiscovery->getLibraryByName(‘tweet’, ‘bootstrap’) (Line: 54)
DrupalCoreAssetLibraryDependencyResolver->doGetDependencies(Array) (Line: 31)
DrupalCoreAssetLibraryDependencyResolver->getLibrariesWithDependencies(Array) (Line: 104)
DrupalCoreAssetAssetResolver->getLibrariesToLoad(Object) (Line: 116)
DrupalCoreAssetAssetResolver->getCssAssets(Object, ) (Line: 291)
DrupalCoreRenderHtmlResponseAttachmentsProcessor->processAssetLibraries(Object, Array) (Line: 161)
DrupalCoreRenderHtmlResponseAttachmentsProcessor->processAttachments(Object) (Line: 45)
DrupalCoreEventSubscriberHtmlResponseSubscriber->onRespond(Object, ‘kernel.response’, Object) (Line: 111)
DrupalComponentEventDispatcherContainerAwareEventDispatcher->dispatch(‘kernel.response’, Object) (Line: 184)
SymfonyComponentHttpKernelHttpKernel->filterResponse(Object, Object, 1) (Line: 166)
SymfonyComponentHttpKernelHttpKernel->handleRaw(Object, 1) (Line: 64)
SymfonyComponentHttpKernelHttpKernel->handle(Object, 1, 1) (Line: 57)
DrupalCoreStackMiddlewareSession->handle(Object, 1, 1) (Line: 47)
DrupalCoreStackMiddlewareKernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupalpage_cacheStackMiddlewarePageCache->pass(Object, 1, 1) (Line: 78)
Drupalpage_cacheStackMiddlewarePageCache->handle(Object, 1, 1) (Line: 47)
DrupalCoreStackMiddlewareReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
DrupalCoreStackMiddlewareNegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
StackStackedHttpKernel->handle(Object, 1, 1) (Line: 652)
DrupalCoreDrupalKernel->handle(Object) (Line: 19)

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/22/feed