v1: MPClient.proc-handle can be None

Fixes:

vllm/v1/engine/core_client.py:196: error: Incompatible types in assignment (expression has type "None", variable has type "EngineCoreProcHandle")  [assignment]

Signed-off-by: Mark McLoughlin <[email protected]>

Author: markmc

vllm/v1/engine/core_client.py

@@ -1,6 +1,6 @@
 import atexit
 import os
-from typing import List
+from typing import List, Optional
 
 import msgspec
 import zmq
@@ -11,7 +11,8 @@
 from vllm.v1.engine import (EngineCoreOutput, EngineCoreOutputs,
                             EngineCoreProfile, EngineCoreRequest,
                             EngineCoreRequestType, EngineCoreRequestUnion)
-from vllm.v1.engine.core import EngineCore, EngineCoreProc
+from vllm.v1.engine.core import (EngineCore, EngineCoreProc,
+                                 EngineCoreProcHandle)
 from vllm.v1.serial_utils import PickleEncoder
 
 logger = init_logger(__name__)
@@ -155,6 +156,7 @@ def __init__(
         self.input_socket.bind(input_path)
 
         # Start EngineCore in background process.
+        self.proc_handle: Optional[EngineCoreProcHandle]
         self.proc_handle = EngineCoreProc.make_engine_core_process(
             *args,
             input_path=