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/search/FindOccurrencesEngine.java
for (int i = 0; i < markers.length; i++) {
					IMarker marker= markers[i];
					Map attributes= marker.getAttributes();
					addSpecialAttributes(attributes);
					marker.setAttributes(attributes);
					addMatch(view, file, marker);
				}
				searchFinished(view);
			}
		};
		run(runnable);
		return null;
	}
	private ISearchResultView startSearch() {
		SearchUI.activateSearchResultView();
		ISearchResultView view= SearchUI.getSearchResultView();
		IJavaElement element= getInput();
		if (view != null) {
			fFinder.searchStarted(view, element.getElementName());
		}
		return view;
	}
	
	private void addMatch(final ISearchResultView view, IResource file, IMarker marker) {
		if (view != null)
			view.addMatch("", getGroupByKey(marker), file, marker); 
	}
	
	private void searchFinished(final ISearchResultView view) {
		if (view != null)