title: NullPointerException when showing JFileChooser
body: <p>I show a JFileChooser with this snippet:</p>
  
  <pre><code>public File getDestination() {
      JFileChooser chooser = new JFileChooser();
      chooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
      int option = chooser.showSaveDialog(null);
      if(option == JFileChooser.APPROVE_OPTION) {
          return chooser.getSelectedFile().getAbsolutePath();
      }
      return new File(".");
  }
  </code></pre>
  
  <p>Usually, the first time it's showed, it displays &amp; works correctly. The second time, it will always throw this exception:</p>
  
  <pre><code>Exception in thread "Basic L&amp;F File Loading Thread" java.lang.NullPointerException
      at sun.awt.shell.Win32ShellFolder2.pidlsEqual(Unknown Source)
      at sun.awt.shell.Win32ShellFolder2.equals(Unknown Source)
      at sun.awt.shell.Win32ShellFolderManager2.isFileSystemRoot(Unknown Source)
      at sun.awt.shell.ShellFolder.isFileSystemRoot(Unknown Source)
      at javax.swing.filechooser.FileSystemView.isFileSystemRoot(Unknown Source)
      at javax.swing.filechooser.WindowsFileSystemView.isTraversable(Unknown Source)
      at javax.swing.JFileChooser.isTraversable(Unknown Source)
      at javax.swing.plaf.basic.BasicDirectoryModel$LoadFilesThread.run0(Unknown Source)
      at javax.swing.plaf.basic.BasicDirectoryModel$LoadFilesThread.run(Unknown Source)
  </code></pre>
  
  <p>Java -version says:</p>
  
  <pre><code>java version "1.6.0_20"
  Java(TM) SE Runtime Environment (build 1.6.0_20-b02)
  Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode, sharing)
  </code></pre>
  
  <p>And the thread I found <a href="http://www.dbvis.com/forum/message.jspa?messageID=10866" rel="nofollow noreferrer">here</a> says I should downgrade the Java version. Should I follow their advice, or is there something I could have done wrong?</p>