Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
*/
    
    void addActivationListener(ICellEditorActivationListener listener) {
        activationListeners.add(listener);
    }
    /**
     * Add columns to the tree and set up the layout manager accordingly.
     */
    private void addColumns() {
        
        TreeColumn[] columns = tree.getColumns();
        for (int i = 0; i < columnLabels.length; i++) {
            String string = columnLabels[i];
            if (string != null) {
                TreeColumn column;
                if (i < columns.length)
                    column = columns[i];
                else
                    column = new TreeColumn(tree, 0);
                column.setText(string);
            }
        }
        tree.addControlListener(new ControlAdapter() {
			public void controlResized(ControlEvent e) {
				Rectangle area = tree.getClientArea();
				TreeColumn[] columns = tree.getColumns();
				columns[0].setWidth(area.width * 40 / 100);
				columns[1].setWidth(area.width - columns[0].getWidth() - 4);
			}
		});