[gnome-software] trivial: Fix a potential crash when sending data from snapd

[Richard Hughes <rhughes src gnome org>]

commit b691ea593b9c418db3f8d752964b997bab1a3a1e
Author: Richard Hughes <richard hughsie com>
Date:   Mon Jul 18 10:10:52 2016 +0100

    trivial: Fix a potential crash when sending data from snapd
    
    Found with clang...

 src/plugins/gs-snapd.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/plugins/gs-snapd.c b/src/plugins/gs-snapd.c
index 1a36d8d..c591a6e 100644
--- a/src/plugins/gs-snapd.c
+++ b/src/plugins/gs-snapd.c
@@ -287,7 +287,7 @@ gs_snapd_request (const gchar  *method,
 
        if (response_type)
                *response_type = g_strdup (soup_message_headers_get_content_type (headers, NULL));
-       if (response) {
+       if (response != NULL && chunk_start != NULL) {
                *response = g_malloc (chunk_length + 2);
                memcpy (*response, chunk_start, chunk_length + 1);
                (*response)[chunk_length + 1] = '\0';