fix List.tree
fix List.tree

it got broken by the last API change of MapIter.new

lucasbuchala/rakudo,teodozjan/rakudo,usev6/rakudo,paultcochrane/rakudo,Leont/rakudo,laben/rakudo,retupmoca/rakudo,cognominal/rakudo,ab5tract/rakudo,ungrim97/rakudo,ungrim97/rakudo,paultcochrane/rakudo,zhuomingliang/rakudo,rakudo/rakudo,rakudo/rakudo,nbrown/rakudo,ab5tract/rakudo,rakudo/rakudo,salortiz/rakudo,cygx/rakudo,ugexe/rakudo,samcv/rakudo,nunorc/rakudo,cygx/rakudo,pmurias/rakudo,b2gills/rakudo,labster/rakudo,Leont/rakudo,tony-o/rakudo,labster/rakudo,paultcochrane/rakudo,zhuomingliang/rakudo,skids/rakudo,azawawi/rakudo,azawawi/rakudo,awwaiid/rakudo,LLFourn/rakudo,salortiz/rakudo,ab5tract/rakudo,labster/rakudo,zostay/rakudo,cognominal/rakudo,awwaiid/rakudo,dwarring/rakudo,softmoth/rakudo,MasterDuke17/rakudo,ungrim97/rakudo,rjbs/rakudo,nbrown/rakudo,sergot/rakudo,sergot/rakudo,samcv/rakudo,sergot/rakudo,b2gills/rakudo,teodozjan/rakudo,teodozjan/rakudo,lucasbuchala/rakudo,sjn/rakudo,azawawi/rakudo,Leont/rakudo,tony-o/rakudo,nbrown/rakudo,retupmoca/rakudo,jonathanstowe/rakudo,LLFourn/rakudo,softmoth/rakudo,ugexe/rakudo,rakudo/rakudo,lucasbuchala/rakudo,raydiak/rakudo,labster/rakudo,dwarring/rakudo,awwaiid/rakudo,nunorc/rakudo,cygx/rakudo,jonathanstowe/rakudo,niner/rakudo,salortiz/rakudo,tony-o/deb-rakudodaily,sjn/rakudo,cognominal/rakudo,ugexe/rakudo,niner/rakudo,dankogai/rakudo,cygx/rakudo,zhuomingliang/rakudo,MasterDuke17/rakudo,nunorc/rakudo,samcv/rakudo,jonathanstowe/rakudo,laben/rakudo,sjn/rakudo,pmurias/rakudo,nbrown/rakudo,skids/rakudo,ugexe/rakudo,usev6/rakudo,usev6/rakudo,b2gills/rakudo,jonathanstowe/rakudo,b2gills/rakudo,dankogai/rakudo,paultcochrane/rakudo,niner/rakudo,rjbs/rakudo,lucasbuchala/rakudo,LLFourn/rakudo,skids/rakudo,rakudo/rakudo,LLFourn/rakudo,tony-o/rakudo,cognominal/rakudo,b2gills/rakudo,tony-o/deb-rakudodaily,teodozjan/rakudo,tbrowder/rakudo,tony-o/deb-rakudodaily,tony-o/deb-rakudodaily,awwaiid/rakudo,MasterDuke17/rakudo,samcv/rakudo,labster/rakudo,dwarring/rakudo,pmurias/rakudo,tony-o/rakudo,softmoth/rakudo,cognominal/rakudo,zostay/rakudo,dankogai/rakudo,ab5tract/rakudo,raydiak/rakudo,ugexe/rakudo,niner/rakudo,softmoth/rakudo,lucasbuchala/rakudo,salortiz/rakudo,retupmoca/rakudo,nbrown/rakudo,Gnouc/rakudo,raydiak/rakudo,dwarring/rakudo,nunorc/rakudo,retupmoca/rakudo,tony-o/rakudo,tbrowder/rakudo,sjn/rakudo,Gnouc/rakudo,awwaiid/rakudo,dankogai/rakudo,tony-o/deb-rakudodaily,tbrowder/rakudo,softmoth/rakudo,dankogai/rakudo,Gnouc/rakudo,rjbs/rakudo,salortiz/rakudo,tony-o/deb-rakudodaily,zostay/rakudo,ungrim97/rakudo,sjn/rakudo,jonathanstowe/rakudo,laben/rakudo,skids/rakudo,usev6/rakudo,skids/rakudo,ungrim97/rakudo,Gnouc/rakudo,Gnouc/rakudo,ab5tract/rakudo,salortiz/rakudo,rakudo/rakudo,MasterDuke17/rakudo,laben/rakudo,paultcochrane/rakudo,tony-o/deb-rakudodaily,cygx/rakudo,usev6/rakudo,azawawi/rakudo,MasterDuke17/rakudo,raydiak/rakudo,nbrown/rakudo,zhuomingliang/rakudo,labster/rakudo,Leont/rakudo,tony-o/rakudo,pmurias/rakudo,azawawi/rakudo,LLFourn/rakudo,Gnouc/rakudo,tbrowder/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,samcv/rakudo,sergot/rakudo,zostay/rakudo