fixed bug in scenery-phet.NumberPicker that was causing multiple timers to be created, giving the appearance of being stuck, most noticeable on iPad
fixed bug in scenery-phet.NumberPicker that was causing multiple timers to be created, giving the appearance of being stuck, most noticeable on iPad

phetsims/scenery-phet,phetsims/scenery-phet,phetsims/scenery-phet