[glib] registrybackend: fix possible crash if cache_node is NULL

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 1b5b0eff9a9d058d6db88109c524c352e118d98f
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Tue Jan 26 12:02:18 2016 +0100

    registrybackend: fix possible crash if cache_node is NULL

 gio/gregistrysettingsbackend.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/gio/gregistrysettingsbackend.c b/gio/gregistrysettingsbackend.c
index a37ffcc..4a8c584 100644
--- a/gio/gregistrysettingsbackend.c
+++ b/gio/gregistrysettingsbackend.c
@@ -673,10 +673,12 @@ static gboolean
 registry_cache_update_node (GNode        *cache_node,
                             RegistryValue registry_value)
 {
-  RegistryCacheItem *cache_item = cache_node->data;
+  RegistryCacheItem *cache_item;
 
   g_return_val_if_fail (cache_node != NULL, FALSE);
-  g_return_val_if_fail (cache_item != NULL, FALSE);
+  g_return_val_if_fail (cache_node->data != NULL, FALSE);
+
+  cache_item = cache_node->data;
 
   if (registry_value.type != cache_item->value.type)
     {