fix(ui): allow null countryCode for phone input

[lesnitsky]

Related Issues

Closes #9811

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[agonhajdari]

Will be most of the time null, because translations will mostly be on language code and not include a countryCode. It would be helpful to check WidgetsBinding.instance.platformDispatcher.locale.countryCode in case Localizations.localeOf(context).countryCode (L93) is null.