avformat/3dostr: Check sample_rate

Fixes: signed integer overflow: -1268324762623155200 * 8 cannot be represented in type 'long'
Fixes: 30123/clusterfuzz-testcase-minimized-ffmpeg_dem_THREEDOSTR_fuzzer-6710765123928064

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/3dostr.c

@@ -103,7 +103,7 @@ static int threedostr_read_header(AVFormatContext *s)
             st->codecpar->codec_type  = AVMEDIA_TYPE_AUDIO;
             st->codecpar->sample_rate = avio_rb32(s->pb);
             st->codecpar->channels    = avio_rb32(s->pb);
-            if (st->codecpar->channels <= 0)
+            if (st->codecpar->channels <= 0 || st->codecpar->sample_rate <= 0)
                 return AVERROR_INVALIDDATA;
             codec                  = avio_rl32(s->pb);
             avio_skip(s->pb, 4);