fix(planner): Use WALK as default directMode if no direct modes specified

Use WALK as default directMode if no direct modes specified. Ensures that results can be found for
transit-only searches.

Author: David Emory

lib/plan/index.js

@@ -63,14 +63,16 @@ app.get('/', function (req, res) {
 
   // construct the R5 query, if applicable
   if (queryR5) {
+    // allow walk as direct mode if none specified
+    const directModes = req.query.directModes.length === 0 ? [ 'WALK' ] : req.query.directModes
     plans.push(r5.requestPlan({
       from,
       to,
       date: req.query.date,
       fromTime: req.query.startTime,
       toTime: req.query.endTime,
       accessModes: req.query.accessModes,
-      directModes: req.query.directModes,
+      directModes: directModes,
       egressModes: req.query.egressModes,
       transitModes: req.query.transitModes,
       bikeTrafficStress: req.query.bikeTrafficStress,