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. 🙏

[nicohrubec]

I'd rather have us test against the real API in this case. We have node integration tests to do that.
Specifically I would just add a graph.invoke(null) to this file:
https://github.com/getsentry/sentry-javascript/blob/develop/dev-packages/node-integration-tests/suites/tracing/langgraph/scenario.mjs

Then we need to update the test.ts in the same folder to check for the spans. Don't think we need the unit tests in this case

[nicohrubec]

@jadengis I opened a PR with how I think we should test this so it fits nicely with the rest of our repo. I hope that's okay (tagged you as co-author so your contribution should still be displayed).

[nicohrubec]

@jadengis Merged the fix! You are added as a co-author and mentioned in the changelog so I hope that's all good. Fix will go out with the next release 10.40.0. Closing this PR