Handle exceptions for read-only files.

[TheHardew]

I played Borderlands GOTY Enhanced, I set the file that controlled the settings to be read-only, because anisotropic filtering would reset upon each launch. On the first launch, nuclues copied this file with the read-only attribute set and when I would change settings in the game, it would cause an unhandled exception to be thrown.

At least I believe that was the cause, I didn't see it any more after removing the attribute, but if you have trouble reproducing, I can try to investigate further.