Can confirm, unfortunately: Running a "Stop Another Command" action will crash VoiceAttack.
Whether the command is running or not does not seem to make a difference, neither does the choice of "Stop selected command" or "Stop by name".
v1.7.2.17 doesn't have this issue, v1.7.2.19 and v1.7.2.20 do(I don't have v1.7.2.18).
EDIT: Fixed in v1.7.2.21