Fix sqlalchemy cache

plugins/sqlalchemy/superduper_sqlalchemy/metadata.py

@@ -111,7 +111,7 @@ def get_metadata_by_identifier(self, type_id, identifier, version):
             return None
         if version is None:
             version = max(metadata.keys())
-        return metadata[version]
+        return metadata.get(version)
 
     def update_metadata(self, metadata):
         self.add_metadata(metadata)