Steps to Reproduce

1. Create two locales one = Locale("en") and two = Locale("en", "")
2. Log both
3. See that one is "en" and two is "en_"

Additional Info and thoughts

This happens on an iOS simulator with the default locale.

I did some research and in this code: https://github.com/flutter/engine/blob/master/lib/ui/window.dart#L511
There should be an additional check if the scriptCode or the _countryCode is an empty string because "en_" is not a valid Unicode BCP47 Locale Identifier