This extension is used when the list is unknown. So if the list is empty or the calling position is not available, shows an error which is Index out of range or null point exception. This extension provides easy usage to get data.

check_data_size_on_list.dart

extension CheckData on List? {
  T getItem<T>(int position,{dynamic errorReturnValue = "."}) => (this?.length ?? 0) > position ? this![position] : errorReturnValue;
}

//USAGE
// var list = [1,2,5,7];
// print("${list[4]}");  this shows index out of range error so now you can use like below
// list.getItem(4) it's return dot because of the default errorReturnValue is .
//
// if you want specify the error value you can enter errorReturnValue parameter
//
// list.getItem(4, errorReturnValue: "there is no value");
//
void main() {
  List? list = [1,3];  
  print("${list.getItem(2, errorReturnValue: "there is no value")}");
}

You can try on dartpad.