I suppose you have earlier messed something up. Try to re-download the master-theme package, extract it into your madde/home/username/themedirectory, run try_it_out.sh once and fill in the details and then do the dpkg-command and report results here. Just to test out the package without actually modifying anything yet.

edit: I got the same error once if I didn't give theme author's details in correct format when asked. Correct format is "Your Name <your@email.com>" without " -characters ofcourse.