Bug 171262 [Dialogs] uncaught NPE in FilteredResourcesSelectionDialog
bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/dialogs/FilteredResourcesSelectionDialog.java
workingSetFilterActionGroup.saveState(memento);
		workingSetFilterActionGroup.dispose();
		StringWriter writer = new StringWriter();
		try {
			memento.save(writer);
			settings.put(WORKINGS_SET_SETTINGS, writer.getBuffer().toString());
		} catch (IOException e) {
			StatusManager.getManager().handle(
					new Status(IStatus.ERROR, WorkbenchPlugin.PI_WORKBENCH,
							IStatus.ERROR, "", e)); 
			
		}
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.dialogs.FilteredItemsSelectionDialog#restoreDialog(org.eclipse.jface.dialogs.IDialogSettings)
	 */
	protected void restoreDialog(IDialogSettings settings) {
		super.restoreDialog(settings);
		boolean showDerived = settings.getBoolean(SHOW_DERIVED);
		showDerivedResourcesAction.setChecked(showDerived);
		this.isDerived = showDerived;
		String setting = settings.get(WORKINGS_SET_SETTINGS);
		if (setting != null) {
			try {
				IMemento memento = XMLMemento.createReadRoot(new StringReader(
						setting));
				workingSetFilterActionGroup.restoreState(memento);
			} catch (WorkbenchException e) {