libavfilter/af_join.c:451: error: Uninitialized Value
  The value read from nb_samples was never initialized.

libavfilter/af_join.c:451:11: 
449.     }
450. 
451.     buf = avfilter_get_audio_buffer_ref_from_arrays(s->data, linesize, perms,
               ^
452.                                                     nb_samples, outlink->format,
453.                                                     outlink->channel_layout);
