Currently you get a stack trace - makes much more sense to launch the console installer.
https://github.com/lucidimagination/izpack/commit/02fe9a3b7675c8ca33fd9af0bbb5ea6fb234d0d3
Thanks, this will be in 4.3.4 as it's ok to be included after the RC1.
I am going to backport to 5 also.
Thanks Julien! I had done a quick scan of my izpack mail but had missed you had already dropped the RC1. That's great, I'll try out.
https://github.com/lucidimagination/izpack/commit/02fe9a3b7675c8ca33fd9af0bbb5ea6fb234d0d3