small fix matching engine AttributeError - object has no attribute #10292

Job	Run time
Python 3.8 extended tests	3m 37s
test with unpublished langchain-core - Python 3.8	59s
Python 3.9 extended tests	3m 37s
Python 3.10 extended tests	3m 35s
test with unpublished langchain-core - Python 3.9	59s
Python 3.11 extended tests	3m 42s
test with unpublished langchain-core - Python 3.10	1m 11s
test with unpublished langchain-core - Python 3.11	59s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.8	1m 11s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.9	1m 6s
compile-integration-tests / Python 3.8	1m 5s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.10	1m 5s
compile-integration-tests / Python 3.9	1m 3s
pydantic-compatibility / Pydantic v1/v2 compatibility - Python 3.11	1m 2s
lint / build (3.8)	2m 33s
compile-integration-tests / Python 3.10	1m 6s
lint / build (3.11)	2m 36s
compile-integration-tests / Python 3.11	1m 2s
test / Python 3.8	1m 3s
test / Python 3.9	3m 15s
test / Python 3.10	1m 10s
test / Python 3.11	1m 14s
	39m 10s

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