[clang] [clang][bytecode] Fix null Descriptor dereference in ArrayElemPtrPop (PR #163386)

[via cfe-commits]

term-est wrote:

> Thank you for the fix, since no one mentioned it in the review, it looks like Timm took care of it when he merged but I w
/anted to mention it to you for the future.
> 
> The summary is normally what goes into the git log and so what is there should cover
> 
> * A description of the problem
> * A description of the solution
> * A description of other important details like specific algorithms or design choices
> 
> Any questions should be made as comments to the PR and they can be addressed as replies.

Hello shafik~

For future reference, do you mind giving me some  ~pointers~ smart pointers so that this wouldn't happen in the future ;_;

```
[clang][Interp] Fix null Descriptor dereference in ArrayElemPtrPop
ByteCode interpretor could deref a null descriptor
when handling typeid (or function pointers) in
ArrayElemPtrPop. We need to treat this case as having no descriptor
```

I had this for the commit message, was it problematic :/

https://github.com/llvm/llvm-project/pull/163386