[PATCH] os: prevent negative array index access (#80890)

[Peter Hutterer]

On Tue, Jul 08, 2014 at 08:12:22AM +0200, Julien Cristau wrote:
> On Tue, Jul  8, 2014 at 09:24:18 +1000, Peter Hutterer wrote:
> 
> > If an empty string is provided to LogMessageVerbSigSafe, the length of the
> > printed string is 0.
> > 
> Do we know who calls this with an empty string?

I couldn't find anything in the server, the reporter claims that the sigsafe
logging test code breaks for him, see
https://bugs.freedesktop.org/show_bug.cgi?id=80890
that's on 1.14.4, not sure how that happens there but tbh I didn't check, I
just fixed the issue I found.

Cheers,
   Peter