Bug 273012 [Forms] NPE in FormPage.setActive(...)
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/forms/editor/FormPage.java
package org.eclipse.ui.forms.editor;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.swt.custom.BusyIndicator;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.*;
import org.eclipse.ui.*;
import org.eclipse.ui.forms.*;
import org.eclipse.ui.forms.widgets.ScrolledForm;
import org.eclipse.ui.part.EditorPart;
/**
 * A base class that all pages that should be added to FormEditor must subclass.
 * Form page has an instance of PageForm that extends managed form. Subclasses
 * should override method 'createFormContent(ManagedForm)' to fill the form with
 * content. Note that page itself can be loaded lazily (on first open).
 * Consequently, the call to create the form content can come after the editor
 * has been opened for a while (in fact, it is possible to open and close the
 * editor and never create the form because no attempt has been made to show the
 * page).
 * 
 * @since 3.0
 */
public class FormPage extends EditorPart implements IFormPage {
	private FormEditor editor;
	private PageForm mform;
	private int index;
	private String id;
	
	private static class PageForm extends ManagedForm {
		public PageForm(FormPage page, ScrolledForm form) {
			super(page.getEditor().getToolkit(), form);