title: Material ui multiple Select
body: <p>this is my code :
  <a href="https://codesandbox.io/embed/material-demo-nxzuy?fontsize=14&amp;hidenavigation=1&amp;theme=dark" rel="noreferrer">Code Sandbox</a></p>
  
  <p>when I select an item from Select component; the value of </p>
  
  <blockquote>
    <p>event.target.value</p>
  </blockquote>
  
  <p>is undefined !!</p>
  
  <p>What is proper implementation?</p>