[goffice] GogObject: fix compilation

[Morten Welinder <mortenw src gnome org>]

commit 3eeb2201f06244fbdfec28db79237e1316d5cf6f
Author: Morten Welinder <terra gnome org>
Date:   Wed Jun 17 16:40:25 2015 -0400

    GogObject: fix compilation

 goffice/graph/gog-object.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/goffice/graph/gog-object.c b/goffice/graph/gog-object.c
index 9ecac45..eb4851c 100644
--- a/goffice/graph/gog-object.c
+++ b/goffice/graph/gog-object.c
@@ -971,7 +971,7 @@ gog_object_generate_name (GogObject *obj)
 
        char const *type_name;
 
-       g_return_val_if_fail (GOG_IS_OBJECT (obj), NULL);
+       g_return_if_fail (GOG_IS_OBJECT (obj));
 
        klass = GOG_OBJECT_GET_CLASS (obj);
        g_return_if_fail (obj->role != NULL);