avformat/matroskadec: Check timescale

Fixes: 3.82046e+18 is outside the range of representable values of type 'unsigned int'
Fixes: 62276/clusterfuzz-testcase-minimized-ffmpeg_dem_WEBM_DASH_MANIFEST_fuzzer-6381436594421760

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit e849eb2343)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/matroskadec.c

@@ -2826,6 +2826,10 @@ static int matroska_parse_tracks(AVFormatContext *s)
                    track->time_scale);
             track->time_scale = 1.0;
         }
+
+        if (matroska->time_scale * track->time_scale > UINT_MAX)
+            return AVERROR_INVALIDDATA;
+
         avpriv_set_pts_info(st, 64, matroska->time_scale * track->time_scale,
                             1000 * 1000 * 1000);    /* 64 bit pts in ns */