Failure in stdlib/tst-arc4random-thread testing glibc 2.41 for release.

[Florian Weimer]

* Cristian Rodríguez:

> On Thu, Jan 16, 2025 at 12:45 PM Florian Weimer <fweimer@redhat.com> wrote:
>
>> Should I send a patch?
>
> Can you add tests and/or actually __libc_fatal() s if this ever
> happens IRL?  getting NULLs is a really nasty failure..

An existing test caught this.  I suppose we can explicitly check for a
zero blob in it, too.

Thanks,
Florian