avformat/tta: Use 64bit intermediate for index

Fixes: signed integer overflow: 42032 * 51092 cannot be represented in type 'int'
Fixes: 26910/clusterfuzz-testcase-minimized-ffmpeg_dem_TTA_fuzzer-6679539648430080

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

libavformat/tta.c

@@ -119,7 +119,7 @@ static int tta_read_header(AVFormatContext *s)
     for (i = 0; i < c->totalframes; i++) {
         uint32_t size = avio_rl32(s->pb);
         int r;
-        if ((r = av_add_index_entry(st, framepos, i * c->frame_size, size, 0,
+        if ((r = av_add_index_entry(st, framepos, i * (int64_t)c->frame_size, size, 0,
                                     AVINDEX_KEYFRAME)) < 0)
             return r;
         framepos += size;