Better fix for GH#1020
Better fix for GH#1020

Let the empty string only suffer from having an iterator created that
doesn't do anything, instead of *all* strings suffering from an extra check.

rakudo/rakudo,nbrown/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,tony-o/rakudo,Gnouc/rakudo,nbrown/rakudo,Gnouc/rakudo,labster/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,tbrowder/rakudo,tbrowder/rakudo,rakudo/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,softmoth/rakudo,salortiz/rakudo,MasterDuke17/rakudo,Gnouc/rakudo,Gnouc/rakudo,tbrowder/rakudo,tony-o/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,nbrown/rakudo,tony-o/rakudo,salortiz/rakudo,nbrown/rakudo,tbrowder/rakudo,rakudo/rakudo,tony-o/rakudo,salortiz/rakudo,rakudo/rakudo,softmoth/rakudo,MasterDuke17/rakudo,softmoth/rakudo,tbrowder/rakudo,labster/rakudo,tony-o/rakudo,softmoth/rakudo,rakudo/rakudo,nbrown/rakudo,tbrowder/rakudo,labster/rakudo,labster/rakudo,MasterDuke17/rakudo,salortiz/rakudo,nbrown/rakudo,tony-o/rakudo,softmoth/rakudo