[poppler] Fix crash in 1026.asan.0.42.pdf

[Thomas Freitag]

Am 17.08.2013 00:02, schrieb Albert Astals Cid:
> Hi guys, i've got more "secret files" crashers. This patch files a crash in
> one called 1026.asan.0.42.pdf
>
> Thomas, guys, can you verify it makes sense? It makes to me, but more eyes
Looks reasonable for me. But I'm not very deep in 
gouraudTriangleShadedFill, but I assume that You regtested it without 
any problem.

Cheers,
Thomas
> better.
>
> Cheers,
>    Albert
>