[llvm] [llvm-c] Add missing nullptr check in LLVMGetFirstDbgRecord (PR #151101)

[Nikita Popov via llvm-commits]

nikic wrote:

For a test, it should be sufficient to just check that the result is null (if there are no debug records). I think all you need to do is create an instruction without debuginfo and then test that calling LLVMGetFirstDbgRecord on it does not crash.

https://github.com/llvm/llvm-project/pull/151101