[libpeas] Fix warning

[Garrett Regier <gregier src gnome org>]

commit 666be5335dbc6b120207ae513d592387a76d9003
Author: Garrett Regier <garrettregier gmail com>
Date:   Tue Nov 12 22:46:41 2013 -0800

    Fix warning

 tests/libpeas/engine.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/tests/libpeas/engine.c b/tests/libpeas/engine.c
index dafe758..7cbff5f 100644
--- a/tests/libpeas/engine.c
+++ b/tests/libpeas/engine.c
@@ -101,7 +101,8 @@ test_engine_get_default (void)
 
   /* Only has a single ref */
   test_engine = peas_engine_get_default ();
-  g_object_add_weak_pointer (test_engine, &test_engine);
+  g_object_add_weak_pointer (G_OBJECT (test_engine),
+                             (gpointer *) &test_engine);
   g_object_unref (test_engine);
   g_assert (test_engine == NULL);