Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
* Selection in the viewer occurred. Check if there is an active cell
     * editor. If yes, deactivate it and check if a new cell editor must be
     * activated.
     * 
     * @param selection
     *            the TreeItem that is selected
     */
    private void handleSelect(TreeItem selection) {
        
        if (cellEditor != null) {
            applyEditorValue();
            deactivateCellEditor();
        }
        
        TreeItem[] sel = new TreeItem[] { selection };
        if (sel.length == 0) {
            setMessage(null);
            setErrorMessage(null);
        } else {
            Object object = sel[0].getData(); 
            if (object instanceof IPropertySheetEntry) {
                
                IPropertySheetEntry activeEntry = (IPropertySheetEntry) object;
                
                setMessage(activeEntry.getDescription());
                
                activateCellEditor(sel[0]);
            }
        }
        entrySelectionChanged();