"No virtual folder, aborting."

I was just starting to use tagging in mutt-kz and used to be able to use the tick (`) to trigger the tag prompt until this week when suddenly it stopped working and I started seeing an error instead: "No virtual folder, aborting." -- I can't figure out what I might have done to bring this on and I can't figure out how to fix it, or even troubleshoot. I tried asking this on Stack Exchange but so far no one has bitten: http://unix.stackexchange.com/questions/273743/why-am-i-getting-no-virtua... The only place I see the error is in this code: https://github.com/karelzak/mutt-kz/blob/master/curs_main.c but I can't quite decifer how I'd be triggering it with "`". My config / setup are at https://gist.github.com/amandabee/cf7faad0a6f2afc485ee I'm at a loss and would love any pointers you can offer me. Thanks! Amanda