accessibility map: check that data is defined for accessiblePlaces

Now that the NodeCollection does not return the 'data' field, when nodes
are retrieved from this collection, the data field will be undefined, so
we make sure to undefined-check it before trying to read
accessiblePlaces data.

packages/transition-common/src/services/accessibilityMap/TransitAccessibilityMapResult.ts

@@ -135,10 +135,14 @@ export class TransitAccessibilityMapResultByNode {
                 continue;
             }
 
+            // FIXME node's 'data' field is not accessible in the frontend
+            // anymore, at least when retrieved from the node collection, so
+            // this feature will not work anymore as long as it is calculated in
+            // the frontend
             const nodeAccessiblePlacesByCategory =
-                nodeAttributes.data.accessiblePlaces?.walking?.placesByTravelTimeByCategory; // TODO: allow stats for other modes
+                nodeAttributes.data?.accessiblePlaces?.walking?.placesByTravelTimeByCategory; // TODO: allow stats for other modes
             const nodeAccessiblePlacesByDetailedCategory =
-                nodeAttributes.data.accessiblePlaces?.walking?.placesByTravelTimeByDetailedCategory;
+                nodeAttributes.data?.accessiblePlaces?.walking?.placesByTravelTimeByDetailedCategory;
             for (let timeMinutes = avgRemainingTimeMinutes; timeMinutes >= 0; timeMinutes--) {
                 if (nodeAccessiblePlacesByCategory) {
                     const accessiblePlacesForTravelTimeByCategory = nodeAccessiblePlacesByCategory[timeMinutes];