Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
tree.setLinesVisible(true);
        tree.setHeaderVisible(true);
        
        addColumns();
        
        hookControl();
        
        treeEditor = new TreeEditor(tree);
        
        createEntryListener();
        createEditorListener();
    }
    /**
     * Activate a cell editor for the given selected tree item.
     * 
     * @param item
     *            the selected tree item
     */
    private void activateCellEditor(TreeItem item) {
        
        tree.showSelection();
        
        IPropertySheetEntry activeEntry = (IPropertySheetEntry) item.getData();
        
        
        cellEditor = activeEntry.getEditor(tree);
        if (cellEditor == null)
            
            return;