[Bugfix][Failing Test] Fix nixl connector test when promt size < block size (#18429)

Signed-off-by: wwl2755 <wangwenlong2755@gmail.com>

vllm/distributed/kv_transfer/kv_connector/v1/nixl_connector.py

@@ -259,6 +259,15 @@ class NixlConnectorScheduler:
         # Loop through scheduled reqs and convert to ReqMeta.
         for req_id, (req, block_ids) in self._reqs_need_recv.items():
             assert req.kv_transfer_params is not None
+            # For the case where there are no remote blocks to pull
+            # (block_ids is empty), we don't need to schedule
+            # an async read on the worker side.
+            if not block_ids:
+                logger.debug(
+                    "Skipping adding request %s to NixlConnectorMetadata, "
+                    "as there are no remote blocks to pull", req_id)
+                continue
+
             meta.add_new_req(
                 request_id=req_id,
                 local_block_ids=block_ids,