Steps to reproduce

1. Configure eZ Publish to work with Solr Storage engine as implemented in EZP-22799.
2. Shut Down Solr Server
3. Try to open eZ Publish front or backend

The whole site will be down and the following fatal error message will be displayed

Fatal error: Uncaught exception 'eZ\Publish\Core\Persistence\Solr\Content\Search\Gateway\HttpClient\ConnectionException' with message 'Could not connect to server http://localhost:8983.'
in /var/www/eZ/530/vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/Persistence/Solr/Content/Search/Gateway/HttpClient/Stream.php:102 Stack trace: #0
/var/www/eZ/530/vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/Persistence/Solr/Content/Search/Gateway/Native.php(157):
eZ\Publish\Core\Persistence\Solr\Content\Search\Gateway\HttpClient\Stream->request('GET', '/solr/select?q=...') #1
/var/www/eZ/530/vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/Persistence/Solr/Content/Search/Handler.php(144):
eZ\Publish\Core\Persistence\Solr\Content\Search\Gateway\Native->findContent(Object(eZ\Publish\API\Repository\Values\Content\Query), Array) #2
/var/www/eZ/530/ezpublish/cache/prod/ezpublishProdProjectContainer.php(18673):
eZ\Publish\Core\Persistence\Solr\Content\Search\Handler->findContent(Object(eZ\Publish\API\Repository\Values\Content\Query),
in /var/www/eZ/530/vendor/ezsystems/ezpublish-kernel/eZ/Publish/Core/Persistence/Solr/Content/Search/Gateway/HttpClient/Stream.php on line 102