Fix bug for calling isEmpty on null object. (#16782)

packages/flutter_localizations/lib/src/material_localizations.dart

@@ -133,8 +133,7 @@ class GlobalMaterialLocalizations implements MaterialLocalizations {
   intl.DateFormat _yearMonthFormat;
 
   static String _computeLocaleName(Locale locale) {
-    final String localeName = locale.countryCode.isEmpty ? locale.languageCode : locale.toString();
-    return intl.Intl.canonicalizedLocale(localeName);
+    return intl.Intl.canonicalizedLocale(locale.toString());
   }
 
   @override

packages/flutter_localizations/test/basics_test.dart

@@ -47,6 +47,28 @@ void main() {
     await tester.pump();
     await tester.pumpWidget(new Container());
   });
+
+  testWidgets('Locale without coutryCode', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/pull/16782
+    await tester.pumpWidget(
+      new MaterialApp(
+        localizationsDelegates: const <LocalizationsDelegate<dynamic>>[
+          GlobalMaterialLocalizations.delegate,
+        ],
+        supportedLocales: const <Locale>[
+          const Locale('es', 'ES'),
+          const Locale('zh'),
+        ],
+        home: new Container(),
+      )
+    );
+
+    await tester.binding.setLocale('zh', null);
+    await tester.pump();
+    await tester.binding.setLocale('es', 'US');
+    await tester.pump();
+
+  });
 }
 
 /// A localizations delegate that does not contain any useful data, and is only