Fix: defensive coding for coordinate format in route suggestion

Author: SamTheCodeBot

src/app/page.tsx

@@ -418,9 +418,14 @@ ${gpxPoints}
         centerLat = selectedStartPoint[1];
         centerLon = selectedStartPoint[0];
       } else if (routes.length > 0) {
-        const allCoords = routes.flatMap(r => r.coordinates);
-        centerLat = allCoords.reduce((sum, [, lat]) => sum + lat, 0) / allCoords.length;
-        centerLon = allCoords.reduce((sum, [lon]) => sum + lon, 0) / allCoords.length;
+        const allCoords = routes.flatMap(r => r.coordinates || []);
+        if (allCoords.length > 0 && Array.isArray(allCoords[0])) {
+          centerLat = allCoords.reduce((sum, coord) => sum + (Array.isArray(coord) ? coord[1] : 0), 0) / allCoords.length;
+          centerLon = allCoords.reduce((sum, coord) => sum + (Array.isArray(coord) ? coord[0] : 0), 0) / allCoords.length;
+        } else {
+          centerLat = 59.3293;
+          centerLon = 18.0686;
+        }
       } else {
         centerLat = 59.3293;
         centerLon = 18.0686;