else:
source = ''
- contributors = ', '.join(person.readable() for person in sorted(set(parsed_dc.technical_editors + parsed_dc.editors)))
+ contributors = ', '.join(person.readable() for person in
+ sorted(set(p for p in (parsed_dc.technical_editors + parsed_dc.editors) if p)))
if contributors:
contributors = "\n\nOpracowanie redakcyjne i przypisy: %s" % contributors
else: