object reference not set to an instance of an object error

Question

I have controller to save record. and my code is as follows

 

[HttpPost]
        public ActionResult CreateP3(Process process)
        {
            var tr = process.StageID + process.PIPENO + process.Status;
            var checkme = (from x in db.Processes
                           where x.StageID + x.PIPENO + x.Status == tr && x.Status == "OK"
                           select x).ToList();
            if (checkme.Count > 0)
            {
                ModelState.AddModelError("PIPENO", "You are trying Duplicate Pipe Entry");
            }
            if (ModelState.IsValid)
            {
                if (process.PipeAl.Order.THK > 1)
                {
                    process.MPP = 20;
                }
                else
                {
                    process.MPP = 1;
                }
                process.CuttingSpeed = (process.ActualMeter*1000)/process.CuttingTime;
                db.Processes.Add(process);
                db.SaveChanges();
                return RedirectToAction("IndexP3");
            }

 But I get object reference not set on an instance of an object error. Pls help