I have this Repository class in the `commonMain`:

class Repository {
    companion object Data {
        var lastUpdate: String? = null
        var countriesListWithSummary: List<CountrySummary> = emptyList()
    }
}

when I compile it for iOS, I get these warnings:

Variable in singleton without @ThreadLocal can't be changed after initialization

Is it something I should fix, and why I get them?