title: ExtJS slider thumb will disappear after click the bar
body: <p>Hi I have a <code>xtype: slider</code>. The thumb will disappear after I click the bar.</p>
  
  <p>I tried to work on sencha fiddle but it works fine.</p>
  
  <p><a href="https://fiddle.sencha.com/#fiddle/11uf" rel="nofollow noreferrer">fiddle sample</a></p>
  
  <p>However the bug will happen in my website</p>
  
  <p><a href="http://ract1436.myweb.hinet.net/samplemvc/" rel="nofollow noreferrer">myweb</a></p>
  
  <p>I do nothing special for my slider object so I have no idea.</p>
  
  <pre><code>xtype: 'slider',
  width: 200,
  value: 0,
  increment: 10,
  minValue: 0,
  maxValue: 100,
  </code></pre>
  
  <p><strong>[UPDATE]</strong></p>
  
  <p>I have updated the fiddle and my website.</p>
  
  <p>There are three kind of thumbs.</p>
  
  <ol>
  <li>fiddle 5.0.1 default image</li>
  </ol>
  
  <p><a href="https://i.stack.imgur.com/nFdqF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nFdqF.png" alt="enter image description here"></a></p>
  
  <ol start="2">
  <li>my 5.0.1 default image</li>
  </ol>
  
  <p><a href="https://i.stack.imgur.com/aJxbS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aJxbS.png" alt="enter image description here"></a></p>
  
  <ol start="3">
  <li>my custom image</li>
  </ol>
  
  <p><a href="https://i.stack.imgur.com/ZD0Ss.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZD0Ss.png" alt="enter image description here"></a></p>
  
  <p>When I click the progress bar the 2,3 will disappear.</p>
  
  <p>Whether I have to link the big size image like 1? Or any other way can fix this problem?</p>