Bug 75711 AstProvider should not create AST if requested by SelectionListenerWithASTManager
3.1 M2 If SelectionListenerWithASTManager waits for an AST and the editor closes we should not create an AST for that one but return null instead.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
private MouseClickListener fMouseListener;
	
	private InformationPresenter fInformationPresenter;
	
	private SelectionHistory fSelectionHistory;
	/**
	 * Indicates whether this editor is about to update any annotation views.
	 * @since 3.0
	 */
	private boolean fIsUpdatingAnnotationViews= false;
	/**
	 * The marker that served as last target for a goto marker request.
	 * @since 3.0
	 */
	private IMarker fLastMarkerTarget= null;
	protected CompositeActionGroup fActionGroups;
	/**
	 * The action group for folding.
	 *  
	 * @since 3.0
	 */
	private FoldingActionGroup fFoldingGroup;
	private CompositeActionGroup fContextMenuGroup;
	/**
	 * Holds the current occurrence annotations.
	 * @since 3.0
	 */
	private Annotation[] fOccurrenceAnnotations= null;
	/**
	 * Tells whether all occurrences of the element at the