[fix] Update bom item description (#11498)

* [fix] Update bom item description

* Update item.py
diff --git a/erpnext/stock/doctype/item/item.py b/erpnext/stock/doctype/item/item.py
index 844d62b..6a6af3d 100644
--- a/erpnext/stock/doctype/item/item.py
+++ b/erpnext/stock/doctype/item/item.py
@@ -91,7 +91,7 @@
 		self.validate_barcode()
 		self.cant_change()
 		self.validate_warehouse_for_reorder()
-		self.update_item_desc()
+		self.update_bom_item_desc()
 		self.synced_with_hub = 0
 
 		self.validate_has_variants()
@@ -599,13 +599,27 @@
 					row.label = label
 					row.description = desc
 
-	def update_item_desc(self):
-		if frappe.db.get_value('BOM',self.name, 'description') != self.description:
-			frappe.db.sql("""update `tabBOM` set description = %s where item = %s and docstatus < 2""",(self.description, self.name))
-			frappe.db.sql("""update `tabBOM Item` set description = %s where
-				item_code = %s and docstatus < 2""",(self.description, self.name))
-			frappe.db.sql("""update `tabBOM Explosion Item` set description = %s where
-				item_code = %s and docstatus < 2""",(self.description, self.name))
+	def update_bom_item_desc(self):
+		if self.is_new(): return
+
+		if self.db_get('description') != self.description:
+			frappe.db.sql("""
+				update `tabBOM`
+				set description = %s
+				where item = %s and docstatus < 2
+			""", (self.description, self.name))
+
+			frappe.db.sql("""
+				update `tabBOM Item`
+				set description = %s
+				where item_code = %s and docstatus < 2
+			""", (self.description, self.name))
+
+			frappe.db.sql("""
+				update `tabBOM Explosion Item`
+				set description = %s
+				where item_code = %s and docstatus < 2
+			""", (self.description, self.name))
 
 	def update_template_item(self):
 		"""Set Show in Website for Template Item if True for its Variant"""