Labeler fails when issue body is empty

[dokimiki]

The problem that is occurring is the same as in #33, but does not appear to have been fixed in the latest version.

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[iba-1]

This is very much needed as #57 is totally breaking this action, and @dokimiki #62 may indeed fix it, is there any way we can get your attention @stephanmiehe?

[stephanmiehe]

Hey folks, I'm on a cruise at the moment but will cut a new release next week when I'm back on keys