flutter - The method 'toLowerCase' was called on null. Receiver: null Tried calling: toLowerCase()

Question

I am getting this error in my code and i dont know how to fix:

The method 'toLowerCase' was called on null.
    Receiver: null
    Tried calling: toLowerCase()

this is where the error is coming from

buildSuggestions(String query){
    final List<UbuildSuggestions(String query){
    final List<UserName> suggestionList = query.isEmpty
        ? []
        : userList.where((UserName user) {
          String _getUsername = user.username.toLowerCase();
          String _query = query.toLowerCase();
          String _getName = user.name.toLowerCase();
          bool matchesUsername = _getUsername.contains(_query);
          bool matchesName = _getName.contains(_query);

          return (matchesUsername || matchesName);
    }).toList();

Answer 1

try

  String _getUsername = (user?.username??"").toLowerCase();
  String _query = (query??"").toLowerCase();
  String _getName = (user?.name??"").toLowerCase();

If the object is null, it will pass the empty string