[clang] [ClANG]Fix block pointer NTTP crash (PR #190377)

[via cfe-commits]

Serosh-commits wrote:

> I don't need the feature personally, and I can't ask anyone to implement it, but the option of allowing it where it's only usable with a null value is not well motivated.
> 
> So either:
> 
>     * Disallow it.
> 
>     * Implement it if you care about it working.

ok then for this pr i should disallow it 
i will try to  implement the full support in another follow up pr for this 

> I don't need the feature personally, and I can't ask anyone to implement it, but the option of allowing it where it's only usable with a null value is not well motivated.
> 
> So either:
> 
>     * Disallow it.
> 
>     * Implement it if you care about it working.

ok no pproblem then i should simply disallow it for now well lets see in follow up other  pr i will try to implement the full feature thanks 

https://github.com/llvm/llvm-project/pull/190377