[clang] [clang][Parser] Pop scope prior VarDecl invalidating by invalid init (PR #77434)

[Ding Fei via cfe-commits]

danix800 wrote:

> This makes sense to me but I would like @cor3ntin to review as well.
> 
> This needs a release note.

Release note is added.

> 
> I see that there was two test cases. Do you think it is worth it to add the second test case as well?

The original testcase from #30908 is added too for completeness.

Please take another look @shafik @cor3ntin 

https://github.com/llvm/llvm-project/pull/77434