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/PreferencePage.java
if (descriptionLabel != null) {
			descriptionLabel.setLayoutData(
				new GridData(GridData.FILL_HORIZONTAL));
		}
		body = createContents(content);
		if (body != null)
			
			body.setLayoutData(new GridData(GridData.FILL_BOTH));
		Composite buttonBar = new Composite(content, SWT.NULL);
		layout = new GridLayout();
		layout.numColumns = 0;
		layout.marginHeight = 0;
		layout.marginWidth = 0;
		buttonBar.setLayout(layout);
		gd = new GridData();
		gd.horizontalAlignment = GridData.END;
		buttonBar.setLayoutData(gd);
		contributeButtons(buttonBar);
		if (createDefaultAndApplyButton) {
			layout.numColumns = layout.numColumns + 2;
			String[] labels = JFaceResources.getStrings(new String[] { "defaults", "apply" }); 
			int heightHint =
				convertVerticalDLUsToPixels(IDialogConstants.BUTTON_HEIGHT);
			int widthHint =
				convertHorizontalDLUsToPixels(IDialogConstants.BUTTON_WIDTH);
			defaultsButton = new Button(buttonBar, SWT.PUSH);
			defaultsButton.setText(labels[0]);
			Dialog.applyDialogFont(defaultsButton);
			GridData data = new GridData(GridData.HORIZONTAL_ALIGN_FILL);
			data.heightHint = heightHint;