matroskadec: Fix bug when parsing realaudio codec parameters

flavor can be 0.

This fixes tract ticket #3214
Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskadec.c

@@ -1803,7 +1803,7 @@ static int matroska_read_header(AVFormatContext *s)
             track->audio.sub_packet_h    = avio_rb16(&b);
             track->audio.frame_size      = avio_rb16(&b);
             track->audio.sub_packet_size = avio_rb16(&b);
-            if (flavor <= 0 || track->audio.coded_framesize <= 0 ||
+            if (flavor < 0 || track->audio.coded_framesize <= 0 ||
                 track->audio.sub_packet_h <= 0 || track->audio.frame_size <= 0 ||
                 track->audio.sub_packet_size <= 0)
                 return AVERROR_INVALIDDATA;