Scenario:
- In script of facet X, (react (stop-when E (react ...)))
- This creates facet Y, child of X.
- Facet X has no endpoints, only its child facet Y.
- When the stop-when fires, without this patch, facet X
will be terminated because the *inner* react above hasn't executed yet.
- With this patch, the check for a useless X is done after the stop-when
has had a chance to run; and so X will survive for now.
Tony Garnock-Jones