Fixed leaking GValue content in clutter_animation_setup_valist().

Normally this leak goes unnoticed because basic fundamental types
are typically used with clutter_actor_animate(), the leak shows up
if boxed or object types are passed (such as ClutterVertex in the
case I stumbled upon).

clutter/clutter-animation.c

@@ -2028,6 +2028,9 @@ clutter_animation_setup_valist (ClutterAnimation *animation,
                                             &final,
                                             pspec,
                                             is_fixed);
+
+
+	  g_value_unset (&final);
         }
 
       property_name = va_arg (var_args, gchar*);