Thanks Roland for the report and Niko for the really helpful debugging. This PNG file is technically non-conformant[1], but strip-nondeterminism should handle it nevertheless. I've changed strip-nondeterminism to stop processing after the IEND chunk and copy through any remaining junk. A new version will be uploaded soon.
Cheers, Andrew [1] see http://www.w3.org/TR/PNG/#15FileConformance item c
