Почему Entity в данном случае может возвращать null?

Почему Entity в данном случае может возвращать null

class SQLiteContext : DbContext
    {
        public DbSet<Employee> Employees { get; set; }
        public SQLiteContext()
        {
            Database.EnsureCreated();
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlite("Data Source=EmployeesDataBase.db");
        }
    }
    class Abc
    {

        SQLiteContext db = new SQLiteContext();
        public List<Employee> GetData()
        {
            List<Employee>? employees = db.Employees.ToList();
            if (employees == null)
                return new();
            return employees;
        }
    }
class Employee
    {
        public Guid Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string PhoneNumber { get; set; }
        public string Description { get; set; }
        public Employee(string firstName, string lastName, string phoneNumber, string description)
        {
            FirstName = firstName;
            LastName = lastName;
            PhoneNumber = phoneNumber;
            Description = description;
            Id = Guid.NewGuid();
        }
    }