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

[Rafael Auler via llvm-commits]

rafaelauler wrote:

This LGTM, I'll defer to @maksfb or @ayermolo to decide whether to fatal on these (refuse to proceed with a proper error message) or just keep processing with a warning like you did.

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