Fix internal server error when calling calendar_ical with empty year
Change suggested by Gobo from Gamingonlinux.com comment section: https://www.gamingonlinux.com/articles/the-gol-website-source-is-now-open-to-everyone.8970/comment_id=83145
Change suggested by Gobo from Gamingonlinux.com comment section: https://www.gamingonlinux.com/articles/the-gol-website-source-is-now-open-to-everyone.8970/comment_id=83145