HttpError: Label does not exist (although it is defined for the project) #60

Related issues #20, #32
Related PRs #57

With issue-labeler version 2.5, I got UnhandledPromiseRejectionWarning: HttpError: Label does not exist warnings but the workflow passed and the PRs got labelled as expected (e.g. andthum/mdtools#138, https://github.com/andthum/mdtools/actions/runs/4076674579/jobs/7024720065).

Now with issue-labeler version 2.6, I get HttpError: Label does not exist errors and the workflow fails, although the PRs still get labelled as expected (e.g. andthum/mdtools#140, https://github.com/andthum/mdtools/actions/runs/4113712400/jobs/7100168530).

I think this behavior change was introduced with PR #57.

My questions:

1. Why does the warning (v2.5) / error (v2.6) pop up at all? The labels have been defined for the repository (https://github.com/andthum/mdtools/labels).
2. What do I have to do to fix the HttpError: Label does not exist error?

If this helps: My issue-labeler config file can be found here and my issue-labeler workflow is defined here.

@balazsorban44: If you have time and the required expertise, could you please help me out? Many thanks!