[patch] Fix crash on NULL rl_prompt

[Tom Tromey]

>>>>> "Pedro" == Pedro Alves <pedro@codesourcery.com> writes:

Pedro> But isn't `rl_prompt' always built from input feed to readline?

Yes.

Pedro> GDB always gives readline a non-NULL prompt, from what I've seen.
Pedro> Hence, I wouldn't be so fast in calling it correct, but I'm
Pedro> not going to spend more time on this.

I see it as defensive programming.

We can always un-approve it, if you would rather wait to see if a
reproducer is available.

Tom