[llvm] [Windows SEH] Fix crash on empty seh block (PR #107031)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

@R-Goc See https://github.com/llvm/llvm-project/blob/main/.github/workflows/email-check.yaml#L29-L39, https://discourse.llvm.org/t/hidden-emails-on-github-should-we-do-something-about-it and https://github.com/settings/emails. (There's an automation workflow that's supposed to detect this and remind you about it, but it seems to not have run here.)

https://github.com/llvm/llvm-project/pull/107031