I wrote:
> Hmm ... that line was last touched by ab1f0c822, so I'm betting that
> I broke it somehow, but I'm not sure how.
> It looks like S_3 might have been parsed from a totally empty source
> string? But if that's the trigger, I'd think it'd be entirely trivial
> to reproduce.
Oh, duh: the reason it's not trivial to reproduce is you have to try
to bind an empty prepared statement *in an already-aborted transaction*.
Will push a fix in a bit.
regards, tom lane