[gdk-pixbuf] jpeg: Prevent crashes when stopping loading broken files

[Bastien Nocera <hadess src gnome org>]

commit 9aa37e998282bcf6b2ac0705345ab2017d4b2c9b
Author: Bastien Nocera <hadess hadess net>
Date:   Tue Dec 5 10:40:44 2017 +0100

    jpeg: Prevent crashes when stopping loading broken files
    
    A follow-up from commit b99e04f, to avoid trying to access pixel data in
    a pixbuf that doesn't exist any more.

 gdk-pixbuf/io-jpeg.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gdk-pixbuf/io-jpeg.c b/gdk-pixbuf/io-jpeg.c
index 1cd3d30..6d9169f 100644
--- a/gdk-pixbuf/io-jpeg.c
+++ b/gdk-pixbuf/io-jpeg.c
@@ -851,7 +851,8 @@ gdk_pixbuf__jpeg_image_stop_load (gpointer data, GError **error)
        cinfo = &context->cinfo;
 
        /* Try to finish loading truncated files */
-       if (cinfo->output_scanline < cinfo->output_height) {
+       if (context->pixbuf &&
+           cinfo->output_scanline < cinfo->output_height) {
                my_src_ptr src = (my_src_ptr) cinfo->src;
 
                /* But only if there's enough buffer space left */