Fix bug in layout index bounds assertion; bug found by flacjacket.
Fix bug in layout index bounds assertion; bug found by flacjacket.

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