title: JS: Failed to execute 'getComputedStyle' on 'Window': parameter is not of type 'Element'
body: <p>In short: I am trying to understand the meaning of this TypeError:
  Failed to execute 'getComputedStyle' on 'Window': parameter 1 is not of type 'Element'
  The error appears while lunching Mediawiki's VisualEditor, as can be seen here:</p>
  
  <p><a href="http://www.wiki.org.il/index.php?title=new-page&amp;veaction=edit" rel="noreferrer">http://www.wiki.org.il/index.php?title=new-page&amp;veaction=edit</a></p>
  
  <p>The error doesn't enables creating new pages or editing the wiki anonymously. 
  However, with the use of a different skin the error disappears:</p>
  
  <p><a href="http://www.wiki.org.il/index.php/Main_Page?useskin=vector" rel="noreferrer">http://www.wiki.org.il/index.php/Main_Page?useskin=vector</a></p>
  
  <p>The wiki runs on 1.25alpha. </p>