Fix empty metadata

Related-Prod: PRODX-0000
Change-Id: I87e7bce4f229fd182e4d40bc236f86076ed1083b
diff --git a/de/heat-templates/scripts/prepare-metadata.py b/de/heat-templates/scripts/prepare-metadata.py
index 93c4cf5..cd592c4 100644
--- a/de/heat-templates/scripts/prepare-metadata.py
+++ b/de/heat-templates/scripts/prepare-metadata.py
@@ -68,6 +68,9 @@
 
     with open(args.metadata_file) as f:
         metadata = yaml.safe_load(f)
+    if not metadata:
+        LOG.info("The metadata is empty")
+        return
     node_meta = get_node_metadata(metadata)
     if node_meta is not None:
         LOG.info(f"Processing node_metadata: {node_meta}")