avutil/frame_copy_audio: also check that channels match

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/frame.c

@@ -614,6 +614,7 @@ static int frame_copy_audio(AVFrame *dst, const AVFrame *src)
     int i;
 
     if (dst->nb_samples     != src->nb_samples ||
+        dst->channels       != src->channels ||
         dst->channel_layout != src->channel_layout)
         return AVERROR(EINVAL);