From 883d41fb40a8eb00438f596337687e8def4577f1 Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Fri, 7 Oct 2016 11:21:18 -0700
Subject: [PATCH] gif2webp: fix crash with NULL extension data

DGifGetExtension() may successfully return, but the data pointer should
still be validated

BUG=webp:310

Change-Id: I6cfe617871fef2fe07887e5f48bb20f7ab7cfb35
(cherry picked from commit 806f6279aef4de8deca01c8e727db4a508716e95)
---
 examples/gif2webp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/examples/gif2webp.c b/examples/gif2webp.c
index b6a9964b..8c0a5851 100644
--- a/examples/gif2webp.c
+++ b/examples/gif2webp.c
@@ -359,6 +359,8 @@ int main(int argc, const char *argv[]) {
         if (DGifGetExtension(gif, &extension, &data) == GIF_ERROR) {
           goto End;
         }
+        if (data == NULL) continue;
+
         switch (extension) {
           case COMMENT_EXT_FUNC_CODE: {
             break;  // Do nothing for now.