title: issue that state is undefined in vuex
body: <p><a href="https://i.stack.imgur.com/52fBK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/52fBK.png" alt="enter image description here" /></a></p>
  <p><a href="https://i.stack.imgur.com/GcJYH.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GcJYH.jpg" alt="enter image description here" /></a></p>
  <p>the error is TypeError: Cannot read property 'state' of undefined</p>