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

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

The issue reporter said that this was a coding error, their issue wasn't about it not being handled but about the fact that the compiler crashed in such cases. Reporting an error here is good enough. It should ideally be reported in Clang but I'd need help from a more knowledgeable contributor to understand why Clang doesn't report this yet and where the fix should be

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