"Non-nullable field..." warning even though the value is ensured to be declared

class Employee
{
    private string _empName;

    public Employee(string name) /*Non-nullable field '_empName' must contain a non-null value when exiting constructor. Consider declaring the field as nullable.*/
    {
        Name = name;
    }

    public string Name
    {
        get { return _empName; }
        set
        {
            if (value?.Length > 15)
            {
                Console.WriteLine("Error! Name cannot exceed 15 characters");
                _empName = String.Empty;
            }
            else
            {
                _empName = value ?? String.Empty;
            }
        }
    }
}