[Bug] BetterDiscord crashes when themes.json is readonly

[FlafyDev]

Describe the Bug

If the file ~/.config/BetterDiscord/data/stable/themes.json is readonly, BetterDiscord crashes on launch.
I assume it occurs with other config files as well.

To Reproduce

0. install BetterDiscord and a theme and enable it.
1. close discord.
2. run chmod -w ~/.config/BetterDiscord/data/stable/themes.json.
3. run discord.
4. wait until discord loads and crashes.

Expected Behavior

I expect for BetterDiscord to be able to handle read-only config files such as themes.json and when it needs to change them, show a message or ignore the request, but not crash.

Discord Version

stable 0.0.18

Additional Context

I'm making a nix home-manager module to declaratively configure BetterDiscord and the files it generates must be read-only. So it generates themes.json as a read-only file and there is nothing I can do about it