[llvm] [AMDGPU][LowerModuleLDS] Avoid crash on zero-sized types (PR #84742)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

I just added a fatal error for now while we figure this out. I think it's better to just avoid crashing in the meantime.

https://github.com/llvm/llvm-project/pull/84742