step1: cloned gallery in my computer
step2: open this project with Android Studio
step3: run "flutter channel master" and "flutter upgrade"
step: run gallery failed
I'm puzzled

Android Studio say:
lib/layout/adaptive.dart:18:55: Error: Getter not found: 'm'.
return getWindowType(context) == AdaptiveWindowType.m;
^
FAILURE: Build failed with an exception.

• Where:
  Script 'E:\flutter\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 900

• What went wrong:
  Execution failed for task ':app:compileFlutterBuildDebug'.

Process 'command 'E:\flutter\flutter\bin\flutter.bat'' finished with non-zero exit value 1

• Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

BUILD FAILED in 31s
Exception: Gradle task assembleDebug failed with exit code 1

who have any idea? very thanks