There's no documentation of behavior of MimeTypesFileTypeMap when malformed mimetype data is
supplied. (via a filename or input stream constructor argument, or via addMimeTypes()). MimeTypeFile, which provides the actual implementation traps exceptions,
and dumps error messages to the console. There's a REMIND commment to 'handle me better'
when the parsing fails

The absence of defined behavior for this 'invalid' case is a JCK testing blocker.