title: Combobox clearing value issue
body: <p>I've stumbled on an issue with Comboboxes in javafx2.2. This is the scenario:</p>
  
  <ul>
  <li>Users click on the 'editFile' button.</li>
  <li>Another pane becomes visible (with the setVisible method). </li>
  </ul>
  
  <p>This pane contains 6 comboboxes.
  Three of them have fixed items: cboReport, cboSales, cboSend. Three of them get their data from a db (ObservableList) and get populated when the pane becomes visible: cboFile, cboCustomer, cboVet</p>
  
  <ul>
  <li>The user selects a file number from the cboFile. The rest of the comboboxes are beeing set with the correct values.</li>
  <li>The user presses the save button, the file gets saved as intended.</li>
  <li>Next the user presses a close button.</li>
  </ul>
  
  <p>When the window closes, the data on the pane gets resetted through a resetGUI_editFilePane() method. There is have lines like:</p>
  
  <pre><code>...
  cboReport.getSelectionModel().clearSelection();
  cboSales.getSelectionModel().clearSelection();
  cboSend.getSelectionModel().clearSelection();
  cboFile.getSelectionModel().clearSelection();
  cboCustomer.getSelectionModel().clearSelection();
  cboVet.getSelectionModel().clearSelection();
  
  cboFile.getItems().clear();
  cboCustomer.getItems().clear();
  cboVet.getItems.clear();
  ...
  </code></pre>
  
  <p>When the user opens the pane again by pressing the 'editFile' button I notice that only the 'fixed item' comboboxes have cleared their selection, the dynamicly filled comboboxes show the last selected item although the value from the selection itself is <code>null</code>. This looks like a graphics bug to me or am I doing something wrong?</p>
  
  <p>Is there any way around this issue or what is the best method to reset a combobox?</p>
  
  <p><strong>EDIT 2014/08/27:</strong><br>
  This is officially not a bug(clearSelection() does not clear value):<br>
  <a href="https://bugs.openjdk.java.net/browse/JDK-8097244" rel="noreferrer">https://bugs.openjdk.java.net/browse/JDK-8097244</a>  </p>
  
  <p>The official "workaround" is to clear the value of the ComboBox after clearing selection.  </p>
  
  <pre><code>cb.getSelectionModel().clearSelection();
  // Clear value of ComboBox because clearSelection() does not do it
  cb.setValue(null);
  </code></pre>