if (ast == null) return null;
	public String getHoverInfo(ITextViewer textViewer, IRegion hoverRegion) {		if (!(getEditor() instanceof JavaEditor))			return null;		IJavaElement je= getEditorInputJavaElement();		if (je == null)			return null;				CompilationUnit ast= JavaPlugin.getDefault().getASTProvider().getAST(je, ASTProvider.WAIT_ACTIVE_ONLY, null);		ASTNode node= NodeFinder.perform(ast, hoverRegion.getOffset(), hoverRegion.getLength());		if (!(node instanceof StringLiteral))			return null;		StringLiteral stringLiteral= (StringLiteral)node;				AccessorClassReference ref= NLSHintHelper.getAccessorClassReference(ast, hoverRegion);		if (ref == null)			return null;				Properties properties= NLSHintHelper.getProperties(je.getJavaProject(), ref.getBinding());				if (properties.isEmpty())			return null;				String value= properties.getProperty(stringLiteral.getLiteralValue(), null);		if (value != null)			value= HTMLPrinter.convertToHTMLContent(value);		else			value= JavaHoverMessages.getString("NLSStringHover.NLSStringHover.missingKeyWarning"); //$NON-NLS-1$				return toHtml(value);	}