perf: Avoid Querying existence of item code

- This should be ensured by Framework.
- It's also there in validate hook.

So no need to do it again for each item.

erpnext/stock/doctype/stock_reconciliation/stock_reconciliation.py

@@ -163,8 +163,8 @@ class StockReconciliation(StockController):
 	def set_current_serial_and_batch_bundle(self, voucher_detail_no=None, save=False) -> None:
 		"""Set Serial and Batch Bundle for each item"""
 		for item in self.items:
-			if not frappe.db.exists("Item", item.item_code):
-				frappe.throw(_("Item {0} does not exist").format(item.item_code))
+			if not item.item_code:
+				continue
 
 			item_details = frappe.get_cached_value(
 				"Item", item.item_code, ["has_serial_no", "has_batch_no"], as_dict=1
@@ -1011,8 +1011,6 @@ class StockReconciliation(StockController):
 			self._cancel()
 
 	def recalculate_current_qty(self, voucher_detail_no, sle_creation, add_new_sle=False):
-		from erpnext.stock.stock_ledger import get_valuation_rate
-
 		for row in self.items:
 			if voucher_detail_no != row.name:
 				continue