The June 2018 release of Calypso, version 0.8.29, has a bug that is triggered by speech input. To avoid this bug, you can do any of the following: (a) deny Chrome access to your microphone, (b) disable your microphone via Sound settings, or (c) don't speak near your microphone while executing a Calypso program.
The fix for this bug will be included in the next Calypso release, due very soon.