Bug 48364 PreferenceDialog can reopen empty
20031209 When you close the Preferences dialog with an entry other than the default selected you will get an empty entry in the dialog when you reopen STEPS 1) Open the preferences dialog 2) Select the Appearances page 3) Close the dialog 4) Reopen - Workbench will be selected and the contents will be empty
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
protected String getSelectedNodePreference() {
		return lastPreferenceId;
	}
	/** 
	 * @param selection the <code>ISelection</code> to examine.
	 * @return the first element, or null if empty.
	 */
	protected IPreferenceNode getSingleSelection(ISelection selection) {
		if (!selection.isEmpty())
			return (IPreferenceNode) ((IStructuredSelection) selection).getFirstElement();
		return null;
	}
	/** 
	 * @return the <code>TreeViewer</code> for this dialog.
	 * @since 3.0
	 */
	protected TreeViewer getTreeViewer() {
		return treeViewer;
	}
	/**
	 * Save the values specified in the pages.
	 * <p>
	 * The default implementation of this framework method saves all
	 * pages of type <code>PreferencePage</code> (if their store needs saving
	 * and is a <code>PreferenceStore</code>).
	 * </p>
	 * <p>
	 * Subclasses may override.
	 * </p>
	 */