[llvm] [BOLT] Fix null pointer dereference in DWP processing with split DWARF (PR #191474)

[Farid Zakaria via llvm-commits]

fzakaria wrote:

> If possible please add test for first assert

I spent a while trying to generate a test that hits the `errs()` but could not.
:(

In the worst case it's a good defensive case that emits a nicer message before doing a SIGSEGV.


https://github.com/llvm/llvm-project/pull/191474