fix(core): Fix error on langgraph resume

[jadengis]

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Closes #19353

[nicohrubec]

Thanks for contributing! Looks good to me, but we'll need to add some tests before merging. Should we take over?

[jadengis]

@nicohrubec Feel free to take over! I would really appreciate the help. This has been burning me in production.

[jadengis]

@nicohrubec Actually nvm I added a test and verified that it fails without the proposed fix. Let me know if this is acceptable. 🙏