[llvm] [yaml2obj] Don't use uninitialized Type (PR #123274)

[Vitaly Buka via llvm-commits]

vitalybuka wrote:

> Couple of thoughts about the test, in addition to the inline comments:
> 
> 1. As we identified when both looking at this, there are two separate cases we may want to consider, namely the case the current test covers (a "Type" field which doesn't start with `SHT_` but also not a recognised other type) and the case you originally identified (a `SHT_` type that isn't a known value, e.g. `SHT_FOO`). We should probably test both of these.
> 2. I don't think you added the case to the right test file. The specific file you added it to was for testing the SectionHeaderTable chunk. It would probably make more sense to add the cases to the `section-type.yaml` file.

Done both.

https://github.com/llvm/llvm-project/pull/123274