[Monorail] Fix empty AC values causing console errors

Change-Id: Iebf3ce1edf620a7ce830ff08ddea18ae2e7bba2f
Reviewed-on: https://chromium-review.googlesource.com/1175414
Commit-Queue: Jeff Carpenter <jeffcarp@chromium.org>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>

appengine/monorail/static/js/tracker/tracker-ac.js

diff --git a/appengine/monorail/static/js/tracker/tracker-ac.js b/appengine/monorail/static/js/tracker/tracker-ac.js
index 6bf2e09..ec516f5 100644
--- a/appengine/monorail/static/js/tracker/tracker-ac.js
+++ b/appengine/monorail/static/js/tracker/tracker-ac.js
@@ -1282,6 +1282,9 @@
 
   allPromises.push(
       fieldsPromise.then(fieldsResponse => {
+        if (Object.keys(fieldsResponse).length === 0) {
+          return {};
+        }
         const jsonData = TKR_convertFields(fieldsResponse);
 
         TKR_setUpUserAutocompleteStores(jsonData.fields);
@@ -1289,9 +1292,12 @@
         return jsonData;
   }));
 
-  // We won't need custom permissions or hotlists later, so there'se no need to
+  // We won't need custom permissions or hotlists later, so there's no need to
   // add them to allPromises.
   customPermissionsPromise.then(customPermissionsResponse => {
+    if (Object.keys(customPermissionsResponse).length === 0) {
+      return {};
+    }
     TKR_setUpCustomPermissionsStore(customPermissionsResponse.permissions);
   });