`CascadiaSettings` is default constructed when human readable error messages are
returned. Even in such cases we need to ensure that all fields are properly
initialized, as a caller might decide to call a `GlobalSettings` getter.
Thus a crash occurred whenever a user was hot-reloading their settings file with
invalid JSON as other code then tried to compare the `GlobalSettings()`.
## PR Checklist
* [x] I work here
* [x] Tests added/passed
## Validation Steps Performed
* Start Windows Terminal and ensure the settings load fine
* Add `"commandline": 123` to any of the generated profiles in settings.json
* The application doesn't crash and shows a warning message
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