Fix bug in Maildir when using non-string subfolders
Fix bug in Maildir when using non-string subfolders

Closes #773

dequis/qtile,tych0/qtile,cortesi/qtile,flacjacket/qtile,cortesi/qtile,jdowner/qtile,tych0/qtile,himaaaatti/qtile,flacjacket/qtile,frostidaho/qtile,himaaaatti/qtile,ramnes/qtile,nxnfufunezn/qtile,dequis/qtile,nxnfufunezn/qtile,rxcomm/qtile,kynikos/qtile,rxcomm/qtile,kynikos/qtile,zordsdavini/qtile,de-vri-es/qtile,de-vri-es/qtile,qtile/qtile,zordsdavini/qtile,qtile/qtile,frostidaho/qtile,soulchainer/qtile,ramnes/qtile,soulchainer/qtile,jdowner/qtile