Bug 37886 Show type hierarchy cancel ends up with empty dialog
1) open type hierarchy on object 2) cancel ->the search is cancelled but an empty dialog is showing up.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/typehierarchy/HierarchyInformationControl.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 java.lang.reflect.InvocationTargetException;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;
import org.eclipse.swt.widgets.Tree;
import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.viewers.AbstractTreeViewer;