[Pharo-project] Traceback from MIMEDocument>>guessTypeFromName

In Pharo1.1 update #11411, evaluating MIMEDocument guessTypeFromName: 'x.css' produces the attached traceback. Changing MIMEDocument>>guessTypeFromName: url "guesses a content type from the url" ^MIMEType forFileNameReturnSingleMimeTypeOrDefault: url asString asURI to MIMEDocument>>guessTypeFromName: url "guesses a content type from the url" ^MIMEType forFileNameReturnSingleMimeTypeOrDefault: url asString (removing asURI), makes it work as expected, answering 'css'. Is this a bug? Is my fix appropriate? I've made this change in my image. What is the process to get this addressed in the product? Thanks, TF