matroskadec: check h in generic rm packet shuffler

Fixes crash

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskadec.c

@@ -2032,7 +2032,7 @@ static int matroska_parse_rm_audio(MatroskaDemuxContext *matroska,
             }
             memcpy(track->audio.buf + y*w, data, w);
         } else {
-            if (size < sps * w / sps) {
+            if (size < sps * w / sps || h<=0) {
                 av_log(matroska->ctx, AV_LOG_ERROR,
                        "Corrupt generic RM-style audio packet size\n");
                 return AVERROR_INVALIDDATA;