Cannot run with sound null safety

[PyMash]

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

• package:simple_animations

For solutions, see https://dart.dev/go/unsound-null-safety

FAILURE: Build failed with an exception.

• Where:
  Script 'C:\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1159

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

Process 'command 'C:\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 31s
Running Gradle task 'assembleDebug'... 92.6s
Exception: Gradle task assembleDebug failed with exit code 1