function getEmployeeDatasetWithNulls() {
  var data = [];
  var employee = hr.db.getSchema().table('Employee');
  var startId = dataGenerator.sampleEmployees.length;
  for (var i = startId; i < startId + 2; i++) {
    var employeeRow = employee.createRow();
    employeeRow.setId('employeeId' + i.toString());
    employeeRow.setHireDate(null);
    data.push(employeeRow);
  }
  return data;
}
Creates two news rows with null hireDate and adds to the sample employees.
@return {!Array<!lf.Row>}