File fix_gifdiff_null_pointer_deref.patch of Package gifsicle

From e2d5c01a9c7022003135888c85b3255226e4cf98 Mon Sep 17 00:00:00 2001
From: Eddie Kohler <ekohler@gmail.com>
Date: Sun, 8 Apr 2018 15:15:56 -0400
Subject: [PATCH] Fix #130 (gifdiff null pointer deref).

---
 src/gifdiff.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/gifdiff.c b/src/gifdiff.c
index ade1e1e..abc0142 100644
--- a/src/gifdiff.c
+++ b/src/gifdiff.c
@@ -61,9 +61,8 @@ static Clp_Parser* clp;
 static void
 combine_colormaps(Gif_Colormap *gfcm, Gif_Colormap *newcm)
 {
-  int i;
-  if (!gfcm) return;
-  for (i = 0; i < gfcm->ncol; i++) {
+  int i, gfcm_ncol = gfcm ? gfcm->ncol : 0;
+  for (i = 0; i < gfcm_ncol; i++) {
     Gif_Color *c = &gfcm->col[i];
     c->pixel = Gif_AddColor(newcm, c, 1);
   }
@@ -116,11 +115,12 @@ apply_image(int is_second, Gif_Stream *gfs, int imageno, uint16_t background)
   uint16_t *data = gdata[is_second];
   uint16_t *last = glast[is_second];
   Gif_Colormap *gfcm = gfi->local ? gfi->local : gfs->global;
+  int gfcm_ncol = gfcm ? gfcm->ncol : 0;
 
   /* set up colormap */
-  for (i = 0; i < gfcm->ncol; ++i)
+  for (i = 0; i < gfcm_ncol; ++i)
     map[i] = gfcm->col[i].pixel;
-  for (i = gfcm->ncol; i < 256; ++i)
+  for (i = gfcm_ncol; i < 256; ++i)
     map[i] = 1;
   if (gfi->transparent >= 0 && gfi->transparent < 256)
     map[gfi->transparent] = TRANSP;