fix mascara warnings

mascara/test/helpers.js

@@ -1,4 +1,4 @@
-function wait (time) {
+export default function wait (time) {
   return new Promise(function (resolve, reject) {
     setTimeout(function () {
       resolve()

mascara/test/test-ui.js

@@ -1,5 +1,3 @@
-const Helper = require('./util/mascara-test-helper.js')
-
 window.addEventListener('load', () => {
   window.METAMASK_SKIP_RELOAD = true
   // inject app container

mascara/test/util/mascara-test-helper.js

@@ -2,15 +2,16 @@ const EventEmitter = require('events')
 const IDB = require('idb-global')
 const KEY = 'metamask-test-config'
 module.exports = class Helper extends EventEmitter {
-  constructor () {
-    super()
-  }
 
   tryToCleanContext () {
     this.unregister()
     .then(() => this.clearDb())
     .then(() => super.emit('complete'))
-    .catch((err) => super.emit('complete'))
+    .catch((err) => {
+      if (err) {
+        super.emit('complete')
+      }
+    })
   }
 
   unregister () {