Crash on launch

[SeZuo]

Tried to download a lot of things and crashed dmodman.

Now this error comes on launch.

thread 'main' panicked at src/cache/file_index.rs:60:103:
called `Option::unwrap()` on a `None` value

I deleted the bad entries from the cache list to be able to launch the app again.

[SeZuo]

https://www.nexusmods.com/witcher3/mods/6621?tab=files&file_id=55648&nmm=1

This is the mod that seems to crash the app reliably with error

thread 'tokio-runtime-worker' panicked at src/cache/file_index.rs:90:71:
called `Option::unwrap()` on a `None` value

[dandels]

This should be fixed as part of the backend rewrite I did for 0.3.0-beta. I uploaded a pre-release that you can try.