fix on default values of variant track options
fix on default values of variant track options

hammerlab/pileup.js,hammerlab/pileup.js,hammerlab/pileup.js,hammerlab/pileup.js,piotr-gawron/pileup.js,piotr-gawron/pileup.js,piotr-gawron/pileup.js,piotr-gawron/pileup.js