Builder: Wrong library loaded in Advanced Open with custom scene file

[kazink]

Steps to reproduce:

1. File -> Open or create new (advanced)
2. Select LBA1, then custom Scene
3. Browse for a Scene.HQR file, and choose 24. Prinsipal Island - Port Belooga
4. Select the same grid: 24. Principal Island - Port Belooga
5. Library can be selected automatically or manually (does not matter), as Islands
6. Click Open
7. The Scene is loaded correctly, but the terrain is garbled - it looks like an LBA2 Library was loaded instead.