Get Object reference not set to an instance of an object in VIEW

Question

Is there anything wrong at the below code? In my VIEW, i got CREATED_DATETIME(have value) in sql result. Somehow I get object reference not set to an instance of an object. I have other page using the same structure function to called VIEW as well and working fine.

using (MyDBEntities entities = new MyDBEntities())
    {
        if (startDate.HasValue && endDate.HasValue)
        {
            result = entities.VIEW_VOID_HISTORY.Where(a => a.CREATED_DATETIME >= startDate.Value && a.CREATED_DATETIME <= endDate.Value).OrderByDescending(a => a.CREATED_DATETIME).ToList();
        }
    }