title: Not able to open "Project Structure" in Android studio
body: <p>I have created new project in studio. Code works fine without any issue.<br>
  But I am facing issue on opening Project Structure.</p>
  
  <p>On click on File -> Project Structure, it's not showing Project Structure dialog
  but, in bottom of studio, it's showing error like below</p>
  
  <pre><code>4:16:06 PM IllegalArgumentException: 
  Multiple entries with same key: 24.0.0 rc4=24.0.0 rc4 and 24.0.0 rc4=24.0.0 rc4
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Fbbw8.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Fbbw8.jpg" alt="IllegalArgumentException error"></a></p>
  
  <p>Can any body know how to solve this issue.
  My Android studio version 2.1.2</p>