fix error for getting None value

Signed-off-by: 0oshowero0 <o0shower0o@outlook.com>

Author: 0oshowero0

transfer_queue/storage/clients/mooncake_client.py

@@ -256,7 +256,7 @@ def _get_bytes_thread_worker(self, batch_keys: list[str], indexes: list[int]) ->
         if len(batch_results) != len(batch_keys):
             raise RuntimeError(f"get_batch returned {len(batch_results)} items, expected {len(batch_keys)}")
 
-        batch_results = [pickle.loads(result) for result in batch_results]
+        batch_results = [pickle.loads(result) if result != b"" else None for result in batch_results]
         results.extend(batch_results)
 
         return results, indexes