Nullable value for non-nullable function call

main.dart

extension NotNullFunctionCall<T> on void Function(T) {
  void maybeCall(T? value) {
    if (value != null) {
      return this.call(value);
    }
  }
}

void navigateTo(int index) {
  print('The index is: $index');
}

class Example {
  const Example({this.index, this.animateTo = navigateTo});

  final int? index;
  final void Function(int) animateTo;

  void run() {
    animateTo.maybeCall(index);
  }
}

Future<void> main() async {
  final example1 = Example(index: 0);
  final example2 = Example();
  
  example1.run(); // will print "The index is: 0"
  example2.run(); // will not print anything as index is null
}