Fix latent type error in Flutter manifest (#20143)

packages/flutter_tools/test/flutter_manifest_test.dart

diff --git a/packages/flutter_tools/test/flutter_manifest_test.dart b/packages/flutter_tools/test/flutter_manifest_test.dart
index 91c42cc..bb24c42 100644
--- a/packages/flutter_tools/test/flutter_manifest_test.dart
+++ b/packages/flutter_tools/test/flutter_manifest_test.dart
@@ -360,6 +360,33 @@
 ''';
       final FlutterManifest flutterManifest = await FlutterManifest.createFromString(manifest);
       expect(flutterManifest.isEmpty, false);
+      expect(flutterManifest.isModule, false);
+      expect(flutterManifest.isPlugin, false);
+      expect(flutterManifest.androidPackage, null);
+    });
+
+    test('allows a module declaration', () async {
+      const String manifest = '''
+name: test
+flutter:
+  module:
+    androidPackage: com.example
+''';
+      final FlutterManifest flutterManifest = await FlutterManifest.createFromString(manifest);
+      expect(flutterManifest.isModule, true);
+      expect(flutterManifest.androidPackage, 'com.example');
+    });
+
+    test('allows a plugin declaration', () async {
+      const String manifest = '''
+name: test
+flutter:
+  plugin:
+    androidPackage: com.example
+''';
+      final FlutterManifest flutterManifest = await FlutterManifest.createFromString(manifest);
+      expect(flutterManifest.isPlugin, true);
+      expect(flutterManifest.androidPackage, 'com.example');
     });
 
     Future<void> checkManifestVersion({