avformat/vividas: Check for EOF in first loop in track_header()

Fixes: timeout (243sec -> a few ms)
Fixes: 25716/clusterfuzz-testcase-minimized-ffmpeg_IO_DEMUXER_fuzzer-5764093666131968

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>
(cherry picked from commit 7170d342e5)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/vividas.c

@@ -293,6 +293,8 @@ static int track_header(VividasDemuxContext *viv, AVFormatContext *s,  uint8_t *
 
     for (i=0;i<val_1;i++) {
         int c = avio_r8(pb);
+        if (avio_feof(pb))
+            return AVERROR_EOF;
         for (j=0;j<c;j++) {
             if (avio_feof(pb))
                 return AVERROR_EOF;