title: git gc - fatal: bad object refs/remotes/Icon
body: <p>My <code>git gc</code> is giving me errors:</p>
  
  <pre><code>error: bad ref for Icon
  fatal: bad object refs/remotes/Icon
  error: failed to run repack
  </code></pre>
  
  <p>I know those <code>Icon</code> files are connected with OS X's auto-created files. 
  I have added them to <code>.gitignore</code>. </p>
  
  <p>But they could have been committed before I did this.</p>
  
  <p>I am the only one who commits / has copy to the repository. </p>
  
  <p>Thank you.</p>