Fix List of S3 bucket for custom endpoint

Signed-off-by: Paolo Di Tommaso <paolo.ditommaso@gmail.com>

plugins/nf-amazon/src/main/nextflow/cloud/aws/nio/S3FileSystemProvider.java

@@ -679,7 +679,11 @@ public <A extends BasicFileAttributes> A readAttributes(Path path, Class<A> type
 				"path must be an instance of %s", S3Path.class.getName());
 		S3Path s3Path = (S3Path) path;
 		if (type.isAssignableFrom(BasicFileAttributes.class)) {
-			return (A) readAttr0(s3Path);
+			return (A) ("".equals(s3Path.getKey())
+					// the root bucket is implicitly a directory
+					? new S3FileAttributes("/", null, 0, true, false)
+					// read the target path attributes
+					: readAttr0(s3Path));
 		}
 		// not support attribute class
 		throw new UnsupportedOperationException(format("only %s supported", BasicFileAttributes.class));