Remove podcast.log errors on first run and fix xsltproc parsing for https feeds

[adam4235]

These changes fix 2 problems:

• Remove the warnings that podcast.log can't be found when the script is run for the first time
• When the RSS feed has an https link, the xsltproc command was giving an error. The example feeds are http but most feeds are https nowadays. This seems to be a known issue in xsltproc:
  https://gitlab.gnome.org/GNOME/libxslt/-/issues/28
  It seemed like maybe a benign problem in the script because, even without xsltproc installed, it still falls back on the use of sed to parse the xml document. Nevertheless, it can be processed with xsltproc by first downloading the xml document with wget, then calling xsltproc on it. According to the above linked issue, that seems to be the correct approach, so I changed bashpodder to do that.