message: indexedDB: use mem storage if db can't connect
diff: @@ -88,10 +88,14 @@ export default class App extends React.Component {
  // actions.analytics.errorEvent(error)
  }
  + try {
  const db = indexedDB.open('test')
  db.onerror = () => {
  window.leveldown = memdown
  }
  + } catch (e) {
  + window.leveldown = memdown
  + }
  setTimeout(() => {
  actions.user.sign()
  