warn when WinePrefixesBasePath is empty

[pt8o]

Resolves https://github.com/Heroic-Games-Launcher/HeroicGamesLauncher/issues/2556

Since all of these settings are saved on edit (rather than waiting for the user to hit a "Save" button or something) I didn't think there was a great way UX-wise to prevent the user from saving an empty folder. Instead I opted to display a warning below the input, and a button to revert to the most recent non-empty path. But the user can still ignore it and save the empty path.

If the user has already saved an empty path and then opens Settings, then there is no recent non-empty path, so the warning still appears but the undo button doesnt.

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Use the following Checklist if you have changed something on the Backend or Frontend:

• [x] Tested the feature and it's working on a current and clean install.
• [x] Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• [ ] Created / Updated Tests (If necessary)
• [ ] Created / Updated documentation (If necessary)