plz update the example with null safety

[samithe7]

}The argument type 'Widget? Function(BuildContext, Map<String, List>)' can't be assigned to the parameter type 'Widget? Function(BuildContext?, Map<String, List>)'.

[Jacky Pan]

Handler defaultHandler = Handler(
    handlerFunc: (BuildContext? context, Map<String, List<String>> params) {
  return YourPageComponent();
});