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
*/
	protected void configureShell(Shell newShell) {
		super.configureShell(newShell);
		newShell.setText(JFaceResources.getString("PreferenceDialog.title")); 
		newShell.addShellListener(new ShellAdapter() {
			public void shellActivated(ShellEvent e) {
				if (lastShellSize == null)
					lastShellSize = getShell().getSize();
			}
		});
	}
	/*(non-Javadoc)
	 * Method declared on Window.
	 */
	protected void constrainShellSize() {
		super.constrainShellSize();
		
		if (lastShellSize == null)
			lastShellSize = getShell().getSize();
	}
	/* (non-Javadoc)
	 * Method declared on Dialog.
	 */
	protected void createButtonsForButtonBar(Composite parent) {
		
		okButton =
			createButton(
				parent,
				IDialogConstants.OK_ID,
				IDialogConstants.OK_LABEL,