Merge pull request #40495 from ruthra-kumar/indexerror_on_err_creation

fix: index error on Exchange Rate Revaluation creation
diff --git a/erpnext/accounts/doctype/exchange_rate_revaluation/exchange_rate_revaluation.py b/erpnext/accounts/doctype/exchange_rate_revaluation/exchange_rate_revaluation.py
index 8be09db..29732ef 100644
--- a/erpnext/accounts/doctype/exchange_rate_revaluation/exchange_rate_revaluation.py
+++ b/erpnext/accounts/doctype/exchange_rate_revaluation/exchange_rate_revaluation.py
@@ -628,21 +628,21 @@
 	if account_balance and (
 		account_balance[0].balance or account_balance[0].balance_in_account_currency
 	):
-		account_with_new_balance = ExchangeRateRevaluation.calculate_new_account_balance(
+		if account_with_new_balance := ExchangeRateRevaluation.calculate_new_account_balance(
 			company, posting_date, account_balance
-		)
-		row = account_with_new_balance[0]
-		account_details.update(
-			{
-				"balance_in_base_currency": row["balance_in_base_currency"],
-				"balance_in_account_currency": row["balance_in_account_currency"],
-				"current_exchange_rate": row["current_exchange_rate"],
-				"new_exchange_rate": row["new_exchange_rate"],
-				"new_balance_in_base_currency": row["new_balance_in_base_currency"],
-				"new_balance_in_account_currency": row["new_balance_in_account_currency"],
-				"zero_balance": row["zero_balance"],
-				"gain_loss": row["gain_loss"],
-			}
-		)
+		):
+			row = account_with_new_balance[0]
+			account_details.update(
+				{
+					"balance_in_base_currency": row["balance_in_base_currency"],
+					"balance_in_account_currency": row["balance_in_account_currency"],
+					"current_exchange_rate": row["current_exchange_rate"],
+					"new_exchange_rate": row["new_exchange_rate"],
+					"new_balance_in_base_currency": row["new_balance_in_base_currency"],
+					"new_balance_in_account_currency": row["new_balance_in_account_currency"],
+					"zero_balance": row["zero_balance"],
+					"gain_loss": row["gain_loss"],
+				}
+			)
 
 	return account_details