Remove the get_video_buffer() callback.

That was never required since avfilter_get_video_buffer() already
calls itself on the next link if get_video_buffer is not defined.

Originally committed as revision 20419 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavfilter/vf_null.c

@@ -23,12 +23,6 @@
 
 #include "avfilter.h"
 
-static AVFilterPicRef *get_video_buffer(AVFilterLink *link, int perms,
-                                        int w, int h)
-{
-    return avfilter_get_video_buffer(link->dst->outputs[0], perms, w, h);
-}
-
 static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
 {
     avfilter_start_frame(link->dst->outputs[0], picref);
@@ -47,7 +41,6 @@ AVFilter avfilter_vf_null = {
 
     .inputs    = (AVFilterPad[]) {{ .name             = "default",
                                     .type             = CODEC_TYPE_VIDEO,
-                                    .get_video_buffer = get_video_buffer,
                                     .start_frame      = start_frame,
                                     .end_frame        = end_frame },
                                   { .name = NULL}},