Bug 41927 [Dialogs] Selecting in PreferenceDialog generates too many invalid entries
20030825 If you select an entry, close the dialog and then reopen it selecting anotehr entry will result in a "this page has invalid values" although you selected nothing.
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceDialog.java
Iterator nodes =
			preferenceManager
				.getElements(PreferenceManager.PRE_ORDER)
				.iterator();
		while (nodes.hasNext()) {
			IPreferenceNode node = (IPreferenceNode) nodes.next();
			IPreferencePage page = node.getPage();
			if (page != null) {
				if (!page.performOk())
					return;
			}
		}
		
		
		handleSave();
		close();
	}
	/**
	 * Selects the page determined by <code>currentTreeItem</code> in
	 * the page hierarchy.
	 */
	private void selectCurrentPageAgain() {
		tree.setSelection(new TreeItem[] { currentTreeItem });
		currentPage.setVisible(true);
	}
	/**
	 * Selects the saved item in the tree of preference pages.
	 * If it cannot do this it saves the first one.
	 */