Fixed main.ts lookup in allDiag  (#4663)
Fixed main.ts lookup in allDiag  (#4663)

* handle missing main.ts

* fixed entrypoint lookup

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