Merge pull request #1359 from gabegorelick/unhandled-promise-warning

fix: unhandled promise warning

lib/queue.js

@@ -842,6 +842,11 @@ Queue.prototype.updateDelayTimer = function() {
         // or the next guard time
         this.delayTimer = setTimeout(() => this.updateDelayTimer(), delay);
       }
+
+      // Silence warnings about promise created but not returned.
+      // This isn't an issue since we emit errors.
+      // See http://bluebirdjs.com/docs/warning-explanations.html#warning-a-promise-was-created-in-a-handler-but-was-not-returned-from-it
+      return null;
     })
     .catch(err => {
       this.emit('error', err, 'Error updating the delay timer');