bugfix: handle singleton in synth.exactly_one
bugfix: handle singleton in synth.exactly_one

tulip-control/tulip-control,tulip-control/tulip-control,necozay/tulip-control,tulip-control/tulip-control,necozay/tulip-control,necozay/tulip-control,tulip-control/tulip-control,necozay/tulip-control,necozay/tulip-control