This commit fixes a bug that caused the Friends page to crash.

The error was a `TypeError` caused by incorrectly accessing the expenses array when calculating friend balances. This has been corrected. The client-side calculation logic is now more robust and handles cases where groups may not have any expenses.

Author: google-labs-jules[bot]

frontend/screens/FriendsScreen.js

@@ -15,9 +15,13 @@ const FriendsScreen = () => {
         const balances = {}; // { friendId: { name, netBalance, groups: { groupId: { name, balance } } } }
 
         groupsWithDetails.forEach(group => {
-            const [members, expenses] = group.details;
+            const [membersResponse, expensesResponse] = group.details;
+            const members = membersResponse.data;
+            const expenses = expensesResponse.data.expenses;
 
-            expenses.expenses.forEach(expense => {
+            if (!expenses) return; // Guard against undefined expenses
+
+            expenses.forEach(expense => {
                 const payerId = expense.createdBy;
                 const payerIsMe = payerId === user._id;