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/ClipboardOperationAction.java
return false;
		}
		return true;
	}
	
		
	private ClipboardData getClipboardData(IJavaElement inputElement, int offset, int length) {
		CompilationUnit astRoot= JavaPlugin.getDefault().getASTProvider().getAST(inputElement, true, null);
		if (astRoot == null) {
			return null;
		}
		
		
		List list= astRoot.imports();
		if (!list.isEmpty()) {
			if (offset < ((ASTNode) list.get(list.size() - 1)).getStartPosition()) {
				return null;
			}
		} else if (astRoot.getPackage() != null) {
			if (offset < ((ASTNode) astRoot.getPackage()).getStartPosition()) {
				return null;
			}
		}
		
		ArrayList res= new ArrayList();
		ImportReferencesCollector collector= new ImportReferencesCollector(new Region(offset, length), res);
		astRoot.accept(collector);
		
		HashSet namesToImport= new HashSet(res.size());
		for (int i= 0; i < res.size(); i++) {