Bug 65268 [projection] editor is missing collapse all action for code folding
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/actions/FoldingActionGroup.java
* 
	 * @return <code>true</code> if the group is enabled
	 */
	protected boolean isEnabled() {
		return fViewer != null;
	}
	
	/*
	 * @see org.eclipse.ui.actions.ActionGroup#dispose()
	 */
	public void dispose() {
		if (isEnabled()) {
			fViewer.removeProjectionListener(fProjectionListener);
			fViewer= null;
		}
		super.dispose();
	}
	
	/**
	 * Updates the actions.
	 */
	protected void update() {
		if (isEnabled()) {
			fToggle.update();
			fToggle.setChecked(fViewer.isProjectionMode());
			fExpand.update();
			fExpandAll.update();
			fCollapse.update();
			fRestoreDefaults.update();
			fCollapseMembers.update();