[epiphany/mcatanzaro/sync-crash] sync: don't crash when message body is empty

[Michael Catanzaro <mcatanzaro src gnome org>]

commit ef0b4177b57fd6ed8d3b24467fa88703c0a6f279
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Sat Jan 11 14:51:36 2020 -0600

    sync: don't crash when message body is empty
    
    I started getting crashes here after I uninstalled glib-networking in my
    jhbuild environment.

 lib/sync/ephy-sync-service.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/lib/sync/ephy-sync-service.c b/lib/sync/ephy-sync-service.c
index 24f5f433d..35e2ccc87 100644
--- a/lib/sync/ephy-sync-service.c
+++ b/lib/sync/ephy-sync-service.c
@@ -919,6 +919,11 @@ get_signed_certificate_cb (SoupSession *session,
   const char *message = NULL;
   const char *certificate = NULL;
 
+  if (!msg->response_body || !msg->response_body->data) {
+    g_warning ("No response body");
+    goto out_error;
+  }
+
   node = json_from_string (msg->response_body->data, &error);
   if (error) {
     g_warning ("Response is not a valid JSON: %s", error->message);