TypeError: Cannot access offset of type string on string in Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension() (line 181 of core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php).

When I enable Bootstrap Styles, then try to open a page for editing, I get this error. If I uninstall Bootstrap Styles, Layout Builder works. But Bootstrap Styles is so cool.

I'm trying to track it down, but could use a pointer if you know what might be happening:

The website encountered an unexpected error. Try again later.

TypeError: Cannot access offset of type string on string in Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension() (line 181 of core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php).
Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions() (Line: 66)
Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss() (Line: 149)
Drupal\Core\Cache\CacheCollector->get() (Line: 44)
Drupal\Core\Asset\LibraryDiscovery->getLibrariesByExtension() (Line: 58)
Drupal\Core\Asset\LibraryDiscovery->getLibraryByName() (Line: 68)
Drupal\Core\Asset\LibraryDependencyResolver->doGetDependencies() (Line: 41)
Drupal\Core\Asset\LibraryDependencyResolver->getLibrariesWithDependencies() (Line: 87)
Drupal\Core\Asset\LibraryDependencyResolver->getMinimalRepresentativeSubset() (Line: 113)
Drupal\Core\Asset\AssetResolver->getLibrariesToLoad() (Line: 131)
Drupal\Core\Asset\AssetResolver->getCssAssets() (Line: 321)
Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAssetLibraries() (Line: 165)
Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAttachments() (Line: 97)
Drupal\big_pipe\Render\BigPipeResponseAttachmentsProcessor->processAttachments() (Line: 45)
Drupal\Core\EventSubscriber\HtmlResponseSubscriber->onRespond()
call_user_func() (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch() (Line: 214)
Symfony\Component\HttpKernel\HttpKernel->filterResponse() (Line: 202)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 43)
Drupal\force_password_change\Service\ForcePasswordChangeRedirectMiddleware->handle() (Line: 58)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 704)
Drupal\Core\DrupalKernel->handle() (Line: 19)