When I go to /blocks/rss_client/managefeeds.php?courseid=1 I get the below output above the page. The page seems to work fine. The warning appears when I have no feeds and also after adding one.

You should set baseurl when using flexible_table.

• line 481 of /lib/tablelib.php: call to debugging()
• line 103 of /blocks/rss_client/managefeeds.php: call to flexible_table->setup()