Bug: The offsets in the header are sometimes wrong

[sehnryr]

Right now, the extraction method implemented follows the specifications shown in #1. But for some files, the offset is wrong by some small amount of bytes, which ultimately make the extraction fail.

For example, the main texture of /Lotus/Weapons/Grineer/Pistols/GrineerLightPistol/GrineerLightPistolPS4_d.png should have an offset of 34081 bytes in the F cache but really have 34079, so 2 bytes less.

One workaround should be to decompress the whole file and get the subset starting from the end of the size of the main texture. This unfortunately increases the complexity of the extraction.