isomp4: fix zero track duration for fragmented mp4

[sscobici]

trak.mdia.mdhd.duration sometimes is 0 for fragmented mp4.
There are two files from Dolby Vision for which video packets cannot be extracted because of that:

• iOS_P5_GlassBlowing2_3840x2160@59.94fps_15200kbps.mp4
• P81_GlassBlowing2_3840x2160@59.94fps_15200kbps_fmp4.mp4

Solution: take duration from trak.tkhd.duration
Please review.

[pdeljanov]

Logic looks good to me. The rustfmt CI is failing because the config requires the nightly toolchain: cargo +nightly fmt. I'll push a commit fixing the clippy errors.

[pdeljanov]

I have fixed the clippy lints in dd61030. You should be able to rebase and force push your PR to clear the CI failures.

[pdeljanov]

Thanks, merged. Seems the CI is a bit broken unfortunately, but I don't think your change will impact any of that.