fixing pio config (guarding against missing yotta config) (#860)
fixing pio config (guarding against missing yotta config) (#860)


switch-education/pxt,switch-education/pxt,switch-education/pxt,Microsoft/pxt,switchinnovations/pxt,switchinnovations/pxt,playi/pxt,switchinnovations/pxt,playi/pxt,playi/pxt,switch-education/pxt,playi/pxt,Microsoft/pxt,Microsoft/pxt,switchinnovations/pxt,switch-education/pxt,Microsoft/pxt,Microsoft/pxt