packetizer: mpeg4video: initialize all callback fields

Signed-off-by: Thomas Guillem <thomas@gllm.fr>

modules/packetizer/mpeg4video.c

@@ -168,6 +168,7 @@ static int Open( vlc_object_t *p_this )
     /* Set callback */
     p_dec->pf_packetize = Packetize;
     p_dec->pf_flush = PacketizeFlush;
+    p_dec->pf_get_cc = NULL;
 
     return VLC_SUCCESS;
 }