s3.c: fix potential null pointer dereference

Fix for scan-build report:

387  (*gb)->prev->next = buf;

     25 Access to field 'next' results in a dereference of a null
        pointer (loaded from field 'prev')

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/s3.c b/src/s3.c
index 65acc52..e6b683b 100644
--- a/src/s3.c
+++ b/src/s3.c
@@ -376,7 +376,7 @@ static int growbuffer_append(growbuffer **gb, const char *data, int dataLen)
             }
             buf->size = 0;
             buf->start = 0;
-            if (*gb) {
+            if (*gb && (*gb)->prev) {
                 buf->prev = (*gb)->prev;
                 buf->next = *gb;
                 (*gb)->prev->next = buf;