Issue #3460900 by DYdave: Typed property '' must not be accessed before initialisation.
https://www.drupal.org/project/s3fs/issues/3460900
Fixed fatal error :
Error: Typed property Drupal\s3fs_bucket\Entity\S3Bucket::$bucket_type must not be accessed before initialization in Drupal\s3fs_bucket\Entity\S3Bucket->getPluginId() (line 123 of modules/contrib/s3fs/modules/s3fs_bucket/src/Entity/S3Bucket.php).
By initializing property $bucket_type
to an empty string.