Fix manifest UI display for manifests with empty layers

Also fixes the command for schema 2 manifests

data/registry_model/shared.py

@@ -12,6 +12,7 @@ from data.registry_model.datatype import FromDictionaryException
 from data.registry_model.datatypes import (RepositoryReference, Blob, TorrentInfo, BlobUpload,
                                            LegacyImage, ManifestLayer, DerivedImage)
 from image.docker.schema1 import ManifestException, DockerSchema1ManifestBuilder
+from image.docker.schema2 import EMPTY_LAYER_BLOB_DIGEST
 
 logger = logging.getLogger(__name__)
 
@@ -344,14 +345,21 @@ class SharedModel:
         working towards the leaf, including the associated Blob and its placements (if specified).
         Returns None if the manifest could not be parsed and validated.
     """
+    retriever = RepositoryContentRetriever(repo_id, storage)
+    requires_empty_blob = parsed.get_requires_empty_layer_blob(retriever)
+
     storage_map = {}
-    if parsed.local_blob_digests:
+    blob_digests = list(parsed.local_blob_digests)
+    if requires_empty_blob:
+      blob_digests.append(EMPTY_LAYER_BLOB_DIGEST)
+
+    if blob_digests:
       blob_query = model.storage.lookup_repo_storages_by_content_checksum(repo_id,
-                                                                          parsed.local_blob_digests,
+                                                                          blob_digests,
                                                                           by_manifest=by_manifest)
       storage_map = {blob.content_checksum: blob for blob in blob_query}
 
-    retriever = RepositoryContentRetriever(repo_id, storage)
+
     layers = parsed.get_layers(retriever)
     if layers is None:
       logger.error('Could not load layers for manifest `%s`', parsed.digest)