Bug 49869 NPE showing Type Hierarchies history after layout change
M6 - I retrieve the org.eclipse.swt project from cvs, though this should happen with any java project - select the project in the Package Explorer and press F4 to open a hierarchy view on it - drop down the hierarchy view's Previous Type Hierarchies tool item, it will show 1+ item(s), good - drop down the hierarchy view's dropdown (ie.- the down-pointing triangle in the toolbar) and select Layout -> Horizontal View Orientation - now try to drop down the Previous Type Hierarchies tool item and the attached exception will occur
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/typehierarchy/HistoryDropDownAction.java
/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
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package org.eclipse.jdt.internal.ui.typehierarchy;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.MenuItem;
import org.eclipse.jface.action.Action;
import org.eclipse.jface.action.ActionContributionItem;
import org.eclipse.jface.action.IMenuCreator;
import org.eclipse.ui.help.WorkbenchHelp;
import org.eclipse.jdt.core.IJavaElement;
import org.eclipse.jdt.internal.ui.IJavaHelpContextIds;
import org.eclipse.jdt.internal.ui.JavaPluginImages;
public class HistoryDropDownAction extends Action implements IMenuCreator {