if ($pi) {
                            $this->site->setPurchaseItem(['id' => $pi->id, 'product_id' => $pi->product_id, 'option_id' => $pi->option_id], $costing->quantity);
                        } else {
                            $pi = $this->site->getPurchasedItem(['product_id' => $costing->product_id, 'option_id' => $costing->option_id ? $costing->option_id : null, 'purchase_id' => null, 'transfer_id' => null, 'warehouse_id' => $sale->warehouse_id]);
                            $this->site->setPurchaseItem(['id' => $pi->id, 'product_id' => $pi->product_id, 'option_id' => $pi->option_id], $costing->quantity);
                        }

change to

                        if ($pi) {
                            $this->site->setPurchaseItem(['id' => $pi->id, 'product_id' => $pi->product_id, 'option_id' => $pi->option_id], $costing->quantity);
                        } else {
                            $pi = $this->site->getPurchasedItem(['product_id' => $costing->product_id, 'option_id' => $costing->option_id ? $costing->option_id : null, 'purchase_id' => null, 'transfer_id' => null, 'warehouse_id' => $sale->warehouse_id]);
                            if($pi)
                                 $this->site->setPurchaseItem(['id' => $pi->id, 'product_id' => $pi->product_id, 'option_id' => $pi->option_id], $costing->quantity);
                        }