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
gd = new GridData();
		gd.horizontalAlignment = GridData.END;
		titleImage.setLayoutData(gd);
		return titleArea;
	}
	/**
	 * Creates a Tree/TreeItem structure that reflects the page hierarchy.
	 */
	private void createTree(Composite parent) {
		if (tree != null)
			tree.dispose();
		tree = new Tree(parent, SWT.BORDER);
		OpenStrategy eventAdapter = new OpenStrategy(tree);
		eventAdapter.addPostSelectionListener(new SelectionAdapter() {
			public void widgetSelected(final SelectionEvent event) {
				BusyIndicator.showWhile(tree.getDisplay(), new Runnable() {
					public void run() {
						Object data = event.item.getData();
						if (data instanceof IPreferenceNode) {
							if (!isCurrentPageValid()) {
								handleError();
							} else if (!showPage((IPreferenceNode) data)) {
								
								handleError();
							} else {
								
								currentTreeItem = (TreeItem) event.item;
							}
							
							tree.setFocus();