fix headsign issue

static/index.html

@@ -273,6 +273,6 @@
       </div>
     </div>
 
-    <script type="module" src="/js/main.js?v=1"></script>
+    <script type="module" src="/js/main.js?v=2"></script>
   </body>
 </html>

static/js/main.js

@@ -168,7 +168,7 @@ function renderVehicle(vehicle) {
           icon: renderVehicleIcon(vehicle),
         })
           .bindPopup(
-            `<b>${routeDesignator(vehicle.route)}</b> to <b>${vehicle.headsign.replace(
+            `<b>${routeDesignator(vehicle.route)}</b> to <b>${vehicle.headsign?.replace(
               /^to /i,
               ""
             )}</b>${vehicle.nearest_station ? `<br />@ ${vehicle.nearest_station?.name}` : ""}<br /><br /><small>vehicle #: ${vehicle.id}</small>`