[glib] Fix GError leak in g_file_query_writable_namespaces()

[Matthias Clasen <matthiasc src gnome org>]

commit 60a6ae6f0b84f059e33b8c658ef22c3d933db0a2
Author: Christophe Fergeau <cfergeau redhat com>
Date:   Sun Mar 29 17:15:15 2015 +0200

    Fix GError leak in g_file_query_writable_namespaces()
    
    gvfs commit b358ca "Make sure metadata is always returned by
    query_writable_namespaces()" changed the
    query_writable_namespaces vfunc to never return NULL, but the error
    checking in g_daemon_file_query_writable_namespaces still assumes vfunc
    failure implies NULL return value and GError set. This causes a memory
    leak as on failure the GError will be set but the vfunc implementation
    will have created its own default list so NULL will not be returned, and
    the GError will never be cleared.
    
    This commit directly checks if the GError is set to detect failures,
    my_error is directly dereferenced in the error block anyway.
    
    This also removes an unneeded call to g_file_attribute_info_new(); as
    the vfunc always returns us a non-NULL GFileAttributeInfoList.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=747364

 gio/gfile.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/gio/gfile.c b/gio/gfile.c
index 0fd62f2..851be01 100644
--- a/gio/gfile.c
+++ b/gio/gfile.c
@@ -4337,9 +4337,14 @@ g_file_query_writable_namespaces (GFile         *file,
 
   if (list == NULL)
     {
+      g_warn_if_reached();
+      list = g_file_attribute_info_list_new ();
+    }
+
+  if (my_error != NULL)
+    {
       if (my_error->domain == G_IO_ERROR && my_error->code == G_IO_ERROR_NOT_SUPPORTED)
         {
-          list = g_file_attribute_info_list_new ();
           g_error_free (my_error);
         }
       else