Flutter AttributeError: 'NoneType' object has no attribute 'x'

Flutter issue

$ flutter channel stable

$ flutter upgrade
(If you are locked in China...终端是这么提示的。需要切换为国内镜像
$ PUB_HOSTED_URL=https://pub.flutter-io.cn

$ export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

$ git clone -b dev https://github.com/flutter/flutter.git

$ export PATH="$PWD/flutter/bin:$PATH"

$ cd ./flutter

$ flutter doctor)

$ cd 工程文件

$ flutter clean

$ flutter run -d device

可以看看这个issue，虽然flutter doctor -v还是标记为 [!]（Flutter & Darts已经安装）

但是可以用终端运行了。