Fix issue accessing a null tagmanifest under a tag in a repository

test/registry/fixtures.py

@@ -13,7 +13,8 @@ from flask import jsonify, g
 from flask_principal import Identity
 
 from app import storage
-from data.database import close_db_filter, configure, DerivedStorageForImage, QueueItem, Image
+from data.database import (close_db_filter, configure, DerivedStorageForImage, QueueItem, Image,
+                           TagManifest)
 from data import model
 from endpoints.csrf import generate_csrf_token
 from util.log import logfile_path
@@ -105,6 +106,10 @@ def registry_server_executor(app):
     namespace_obj.save()
     return 'OK'
 
+  def delete_manifests():
+    TagManifest.delete().execute()
+    return 'OK'
+
   executor = LiveServerExecutor()
   executor.register('generate_csrf', generate_csrf)
   executor.register('set_supports_direct_download', set_supports_direct_download)
@@ -118,6 +123,7 @@ def registry_server_executor(app):
   executor.register('reload_app', reload_app)
   executor.register('create_app_repository', create_app_repository)
   executor.register('disable_namespace', disable_namespace)
+  executor.register('delete_manifests', delete_manifests)
   return executor