avcodec/codec_par: do not copy AVChannelLayout struct directly

Later we use av_channel_layout_copy, but that uninits the struct
unintentionally freeing the possibly allocated u.map pointer.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavcodec/codec_par.c

@@ -78,6 +78,7 @@ int avcodec_parameters_copy(AVCodecParameters *dst, const AVCodecParameters *src
     codec_parameters_reset(dst);
     memcpy(dst, src, sizeof(*dst));
 
+    dst->ch_layout      = (AVChannelLayout){0};
     dst->extradata      = NULL;
     dst->extradata_size = 0;
     if (src->extradata) {