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
/* (non-Javadoc)
	 * @see org.eclipse.jdt.internal.ui.text.JavaOutlineInformationControl#createTreeViewer(org.eclipse.swt.widgets.Composite, int)
	 */
	protected TreeViewer createTreeViewer(Composite parent, int style) {
		Tree tree= new Tree(parent, SWT.SINGLE | (style & ~SWT.MULTI));
		tree.setLayoutData(new GridData(GridData.FILL_BOTH));
		TreeViewer treeViewer= new TreeViewer(tree);
		treeViewer.addFilter(new ViewerFilter() {
			public boolean select(Viewer viewer, Object parentElement, Object element) {
				return element instanceof IType;
			}
		});		
		
		fLifeCycle= new TypeHierarchyLifeCycle(false);
		treeViewer.setSorter(new HierarchyViewerSorter(fLifeCycle));
		treeViewer.setAutoExpandLevel(AbstractTreeViewer.ALL_LEVELS);
		fLabelProvider= new HierarchyInformationControlLabelProvider(fLifeCycle);
		fLabelProvider.setTextFlags(JavaElementLabels.ALL_DEFAULT | JavaElementLabels.T_POST_QUALIFIED);
		treeViewer.setLabelProvider(new DecoratingJavaLabelProvider(fLabelProvider, true, false));	
		
		return treeViewer;
	}
	
	/* (non-Javadoc)
	 * @see org.eclipse.jdt.internal.ui.text.AbstractInformationControl#setForegroundColor(org.eclipse.swt.graphics.Color)
	 */
	public void setForegroundColor(Color foreground) {
		super.setForegroundColor(foreground);
		fLabel.setForeground(foreground);