expired ids should reject instead of returning null

server/server.js

@@ -117,7 +117,7 @@ app.get('/download/:id', (req, res) => {
   }
 
   storage.filename(id).then(filename => {
-    storage
+    return storage
       .length(id)
       .then(contentLength => {
         storage.ttl(id).then(timeToExpiry => {
@@ -128,11 +128,11 @@ app.get('/download/:id', (req, res) => {
             timeToExpiry: timeToExpiry
           });
         });
+      });
   })
   .catch(() => {
     res.status(404).render('notfound');
-      });
-  });
+  });;
 });
 
 app.get('/assets/download/:id', (req, res) => {

server/storage.js

@@ -90,11 +90,10 @@ function ttl(id) {
 function filename(id) {
   return new Promise((resolve, reject) => {
     redis_client.hget(id, 'filename', (err, reply) => {
-      if (!err) {
-        resolve(reply);
-      } else {
-        reject(err);
+      if (err || !reply) {
+        return reject();
       }
+      resolve(reply);
     });
   });
 }