Merge pull request #50084 from Expensify/jasper-fixDuplicateWaypointE…

…rror

[CP Staging] Ensure that round trips do not display the duplicate waypoint error incorrectly

(cherry picked from commit c7c8cd6)

(CP triggered by jasperhuangg)

src/libs/TransactionUtils/index.ts

@@ -646,7 +646,10 @@ function getValidWaypoints(waypoints: WaypointCollection | undefined, reArrangeI
     let waypointIndex = -1;
 
     return waypointValues.reduce<WaypointCollection>((acc, currentWaypoint, index) => {
-        const previousWaypoint = waypointValues.at(lastWaypointIndex);
+        // Array.at(-1) returns the last element of the array
+        // If a user does a round trip, the last waypoint will be the same as the first waypoint
+        // We want to avoid comparing them as this will result in an incorrect duplicate waypoint error.
+        const previousWaypoint = lastWaypointIndex !== -1 ? waypointValues.at(lastWaypointIndex) : undefined;
 
         // Check if the waypoint has a valid address
         if (!waypointHasValidAddress(currentWaypoint)) {