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 final TextOperationAction fTextOperationAction;
		
		/**
		 * Creates a dispatch action.
		 * 
		 * @param resourceBundle the resource bundle
		 * @param prefix the prefix
		 * @param textOperationAction the text operation action
		 */
		public InformationDispatchAction(ResourceBundle resourceBundle, String prefix, final TextOperationAction textOperationAction) {
			super(resourceBundle, prefix, JavaEditor.this);
			if (textOperationAction == null)
				throw new IllegalArgumentException();
			fTextOperationAction= textOperationAction;
		}
		
		/*
		 * @see org.eclipse.jface.action.IAction#run()
		 */
		public void run() {
			/**
			 * Information provider used to present the information.
			 * 
			 * @since 3.0
			 */
			class InformationProvider implements IInformationProvider, IInformationProviderExtension2 {