title: when click back button navigated to every pages I visit
body: <p>I have 5 screens.</p>
  
  <p>The 5th screen has a button go to the 1st screen.</p>
  
  <p>I clicked the 1st screen and 2nd screen and 3rd screen and 4th screen and 5th screen again clicked the 1st screen and 2nd screen and 3rd screen and 4th screen and 5th screen. (1>2>3>4>5>1>2>3>4>5)</p>
  
  <p>I clicked back button again and again.not stopping in 1st page. go to I visited every page. (5&lt;4&lt;3&lt;2&lt;1&lt;5&lt;4&lt;3&lt;2&lt;1)</p>
  
  <p>I used <code>WillPopScope</code></p>