[Bug Report] Rescanning windows on *nix paths breaks galleries

[feederbox826]

Describe the bug Gallery paths are prepended instead of replaced on rescan when moving from Windows to *nix

To Reproduce Steps to reproduce the behavior:

1. Import a gallery on windows at D:/stash/gallery.zip
2. Migrate to *nix, data is now at /mnt/stash
3. Scan disk - gallery is discovered

Expected behavior Previous windows path is replaced by new *nix path

Instead the windows path is appended

internal error getting relative path: Rel: can't make D:\stash\gallery.zip/0001.jpg relative to /mnt/stash/gallery.zip

Stash Version: (from Settings -> About): v0.26.0 reproducible up to v0.26.2-35-g4cca3b29 develop

Additional context I looked through the go source but was frankly quite lost :( This has been reported multiple times on the discord, I figured I would actually investigate it