Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
* not visible in the viewer.
     * 
     * @return the root entry or <code>null</code>.
     */
    public IPropertySheetEntry getRootEntry() {
        return rootEntry;
    }
    /**
     * The <code>PropertySheetViewer</code> implementation of this
     * <code>ISelectionProvider</code> method returns the result as a
     * <code>StructuredSelection</code>.
     * <p>
     * Note that this method only includes <code>IPropertySheetEntry</code> in
     * the selection (no categories).
     * </p>
     */
    public ISelection getSelection() {
        if (tree.getSelectionCount() == 0)
            return StructuredSelection.EMPTY;
        TreeItem[] sel = tree.getSelection();
        List entries = new ArrayList(sel.length);
        for (int i = 0; i < sel.length; i++) {
            TreeItem ti = sel[i];
            Object data = ti.getData();
            if (data instanceof IPropertySheetEntry)
                entries.add(data);
        }
        return new StructuredSelection(entries);
    }
    /**