颤动。如何在GridView.builder为空时折叠它(没有任何元素)

import 'package:flutter/material.dart';

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  bool _isExpanded = false;

  @override
  Widget build(BuildContext context) {
    return ListView(
      children: [
        ExpansionPanelList(
          elevation: 1,
          expandedHeaderPadding: EdgeInsets.zero,
          expansionCallback: (int index, bool isExpanded) {
            setState(() {
              _isExpanded = !isExpanded;
            });
          },
          children: [
            ExpansionPanel(
              headerBuilder: (BuildContext context, bool isExpanded) {
                return ListTile(
                  title: Text('GridView'),
                );
              },
              body: _isExpanded
                  ? GridView.builder(
                      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                        crossAxisCount: 2,
                      ),
                      itemCount: 0, // 设置为0，即为空
                      itemBuilder: (BuildContext context, int index) {
                        return Container(
                          color: Colors.grey,
                          margin: EdgeInsets.all(8),
                        );
                      },
                    )
                  : Container(),
              isExpanded: _isExpanded,
            ),
          ],
        ),
      ],
    );
  }
}