Avformat: don't warn about AVCODEC_ID_NONE tracks
Avformat: don't warn about AVCODEC_ID_NONE tracks

(cherry picked from commit 37e7db4956c0e5605ce207435ac81a7be0ef0d53)
Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@videolan.org>

jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2