fix: Skip empty rows while updating unsaved BOM cost (#28136) (#28141)

- Dont try to get valuation rate if row has no item code
- Dont try to add exploded items if row has no item code

(cherry picked from commit 292419bc9e)

Co-authored-by: Marica <maricadsouza221197@gmail.com>

erpnext/manufacturing/doctype/bom/bom.py

@@ -240,6 +240,9 @@ class BOM(WebsiteGenerator):
 		existing_bom_cost = self.total_cost
 
 		for d in self.get("items"):
+			if not d.item_code:
+				continue
+
 			rate = self.get_rm_rate({
 				"company": self.company,
 				"item_code": d.item_code,
@@ -549,7 +552,7 @@ class BOM(WebsiteGenerator):
 		for d in self.get('items'):
 			if d.bom_no:
 				self.get_child_exploded_items(d.bom_no, d.stock_qty)
-			else:
+			elif d.item_code:
 				self.add_to_cur_exploded_items(frappe._dict({
 					'item_code'		: d.item_code,
 					'item_name'		: d.item_name,