[gom] repository: Add missing annotation

[Mathieu Bridon <mbridon src gnome org>]

commit a91010ac26bf2f698f052eba0626a84a734f7eb6
Author: Mathieu Bridon <bochecha daitauha fr>
Date:   Sun Jul 5 11:32:21 2015 +0200

    repository: Add missing annotation
    
    The function allows the filter to be NULL.
    
    But without this annotation, not only is the documentation wrong,
    gobject-introspection will also refuse a None value when calling the
    function from Python.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=751977

 gom/gom-repository.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gom/gom-repository.c b/gom/gom-repository.c
index bfa196a..28e723c 100644
--- a/gom/gom-repository.c
+++ b/gom/gom-repository.c
@@ -710,7 +710,7 @@ gom_repository_find_one_cb (GObject      *object,
  * gom_repository_find_one_sync:
  * @repository: (in): A #GomRepository.
  * @resource_type: (in): A #GType of the resource to lookup.
- * @filter: (in): A #GomFilter to apply to your search.
+ * @filter: (in) (allow-none): A #GomFilter to apply to your search.
  * @error: (out): A location for a #GError, or %NULL.
  *
  * Synchronous version of gom_repository_find_async().