Please update Example #179

Error: Cannot run with sound null safety, because the following dependencies
don't support null safety:

• package:mp_chart
• package:path_drawing
• package:optimized_gesture_detector
• package:path_provider
• package:screenshot
• package:platform
• package:path_parsing

For solutions, see https://dart.dev/go/unsound-null-safety
/G:/AAAInstallation/src/flutter/.pub-cache/hosted/pub.dartlang.org/mp_chart-0.3.1/lib/mp/chart/chart.dart:51:12: Error: The method 'then' isn't defined for the class 'FutureOr'.
Try correcting the name to the name of an existing method, or defining a method named 'then'.
.then((value) {
^^^^
/G:/AAAInstallation/src/flutter/.pub-cache/hosted/pub.dartlang.org/mp_chart-0.3.1/lib/mp/core/utils/painter_utils.dart:15:34: Error: The getter 'text' isn't defined for the class 'InlineSpan'.

• 'InlineSpan' is from 'package:flutter/src/painting/inline_span.dart' ('/G:/AAAInstallation/src/flutter/packages/flutter/lib/src/painting/inline_span.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'text'.
  var preText = painter.text.text;
  ^^^^
  /G:/AAAInstallation/src/flutter/.pub-cache/hosted/pub.dartlang.org/optimized_gesture_detector-0.0.6/lib/scale.dart:229:40: Error: Couldn't find constructor 'VelocityTracker'.
  _velocityTrackers[event.pointer] = VelocityTracker(event.kind);
  ^^^^^^^^^^^^^^^
  /G:/AAAInstallation/src/flutter/.pub-cache/hosted/pub.dartlang.org/platform-2.2.1/lib/src/interface/local_platform.dart:45:41: Error: Member not found: 'packageRoot'.
  String get packageRoot => io.Platform.packageRoot;
  ^^^^^^^^^^^

FAILURE: Build failed with an exception.

• Where:
  Script 'G:\AAAInstallation\src\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1159

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

Process 'command 'G:\AAAInstallation\src\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 1m 1s
Exception: Gradle task assembleDebug failed with exit code 1