[js] Fix bug in nqp::p6store.
[js] Fix bug in nqp::p6store.

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