[glib] docs: improve doc of g_file_info_list_attributes()

[Sébastien Wilmet <swilmet src gnome org>]

commit a4ed89bf75190631087596be22f9eb10dc6e53ef
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Apr 15 14:53:16 2015 +0200

    docs: improve doc of g_file_info_list_attributes()
    
    The name_space can be NULL.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=747927

 gio/gfileinfo.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gio/gfileinfo.c b/gio/gfileinfo.c
index 7711416..15abe79 100644
--- a/gio/gfileinfo.c
+++ b/gio/gfileinfo.c
@@ -616,7 +616,8 @@ g_file_info_has_namespace (GFileInfo  *info,
 /**
  * g_file_info_list_attributes:
  * @info: a #GFileInfo.
- * @name_space: a file attribute key's namespace.
+ * @name_space: (nullable): a file attribute key's namespace, or %NULL to list
+ *   all attributes.
  *
  * Lists the file info structure's attributes.
  *