mail/rss2email2: Add workaround for filtering out bad tags

This can apparently be triggered with malformed RSS feeds.

Traceback (most recent call last):

File "/usr/share/rss2email/rss2email.py", line 711, in run
  tagline = ",".join(taglist)

TypeError: sequence item 1: expected string or Unicode, NoneType found

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=734327

• Reset maintainer due to the long timeout

PR: 214934
Submitted by: jonathan@invertedearth.net
Approved by: srg@guglielmo.us (maintainer timeout, ~2 years)