another default

panda/src/audio/audio_gui_functor.h

@@ -16,7 +16,8 @@ protected:
 public:
   virtual void doit(GuiBehavior*);
 PUBLISHED:
-  AudioGuiFunctor(AudioSound*, GuiBehavior::BehaviorFunctor* =
+  AudioGuiFunctor(AudioSound* = (AudioSound*)0L,
+		  GuiBehavior::BehaviorFunctor* =
 		  (GuiBehavior::BehaviorFunctor*)0L);
   virtual ~AudioGuiFunctor(void);
   INLINE AudioSound* get_sound(void) const { return _sound; }