Flutter 引发了另一个异常：RenderBox未布局：RenderPaintBoundary#a0069 NEEDS-LAYOUT NEEDS-PAINT

我有以下颤振布局，问题是我得到了一个错误的说法：

引发了另一个异常：RenderBox未布局：RenderPaintBoundary#a0069 NEEDS-LAYOUT NEEDS-PAINT

当我移除扩展的小部件并用一个具有固定高度的容器替换它时，一切正常，但我不希望这样，因为我不知道最终列表中有多少项，所以我无法确定它的固定高度

@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: CustomAppBar(pageTitle: ' انشاء طلب'),
      body: Stack(
        children: [
          AppBackgroundImage(),
          SingleChildScrollView(
            child: Padding(
              padding: const EdgeInsets.fromLTRB(20.0, 0.0, 20.0, 0.0),
              child: Card(
                child: Padding(
                  padding: const EdgeInsets.symmetric(
                      vertical: 30.0, horizontal: 10.0),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.stretch,
                    children: [
                      Text(
                        'ملفات الطلب',
                        style: TextStyle(
                          fontSize: 18.0,
                        ),
                      ),
                      Align(
                        alignment: Alignment.centerRight,
                        child: FlatButton(
                          color: Colors.blueGrey[700],
                          onPressed: () => _openFileExplorer(),
                          child: Text(
                            'رفع الملف',
                            style: TextStyle(
                              color: Colors.white,
                            ),
                          ),
                        ),
                      ),
                      Builder(
                        builder: (BuildContext context) => _loadingPath
                            ? Padding(
                                padding: const EdgeInsets.only(bottom: 10.0),
                                child: const CircularProgressIndicator(),
                              )
                            : _paths != null
                                ? Expanded(
                                    child: ListView.separated(
                                      physics: NeverScrollableScrollPhysics(),
                                      itemCount:
                                          _paths != null && _paths.isNotEmpty
                                              ? _paths.length
                                              : 1,
                                      itemBuilder:
                                          (BuildContext context, int index) {
                                        final bool isMultiPath =
                                            _paths != null && _paths.isNotEmpty;
                                        final String name = 'Choosen File: ' +
                                            (isMultiPath
                                                ? _paths
                                                    .map((e) => e.name)
                                                    .toList()[index]
                                                : _fileName ?? '...');
                                        final path = _paths
                                            .map((e) => e.path)
                                            .toList()[index]
                                            .toString();

                                        return ListTile(
                                          title: Text(
                                            name,
                                          ),
                                        );
                                      },
                                      separatorBuilder:
                                          (BuildContext context, int index) =>
                                              const Divider(),
                                    ),
                                  )
                                : const SizedBox(),
                      ),
                      SizedBox(
                        height: 30.0,
                      ),
                      fileLanguage(context),
                      SizedBox(
                        height: 30.0,
                      ),
                      translateLanguage(context),
                      SizedBox(
                        height: 30.0,
                      ),
                      majors(context),
                      SizedBox(
                        height: 30.0,
                      ),
                      nextButton(context),
                      SizedBox(
                        height: 30.0,
                      ),
                    ],
                  ),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }