Make sure that an AlertDialog doesn't crash in 0x0 environment (flutter#174091)

This is my attempt to handle
flutter#6537 for the AlertDialog UI
control.

Author: ahmedsameha1

packages/flutter/test/material/dialog_test.dart

@@ -3021,6 +3021,17 @@ void main() {
     expect(find.byType(BackButton), findsNothing);
     expect(find.byType(CloseButton), findsOneWidget);
   });
+
+  testWidgets('AlertDialog does not crash at zero area', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Center(
+          child: SizedBox.shrink(child: AlertDialog(content: Text('X'))),
+        ),
+      ),
+    );
+    expect(tester.getSize(find.byType(AlertDialog)).isEmpty, isTrue);
+  });
 }
 
 @pragma('vm:entry-point')