title: heroku can't deploy but it's not any error message?
body: <p><a href="https://github.com/unnhao/ReactRealTimeChatTraining" rel="nofollow noreferrer">https://github.com/unnhao/ReactRealTimeChatTraining</a></p>
  
  <p>i deploy to heroku, it didn't occur any error at build log</p>
  
  <p>but when i want to access this <a href="https://moutalk.herokuapp.com/" rel="nofollow noreferrer">https://moutalk.herokuapp.com/</a>
  it display Application error</p>
  
  <p>i test for github </p>
  
  <p>git clone 
  npm install
  npm start</p>
  
  <p>but it can run!!!</p>
  
  <p>what's happen???</p>