Sorry about that, we caught this in 1.8.0 and 1.7.8.4 for Unity 4.x, but it looks like somehow it got into 1.7.8.4 for Unity 5.x.
The "proper" version of the action has a Finish checkbox that defaults to false to preserve the original behaviour. We work to preserve the original behaviour when updating actions, but sometimes something slips through. We also consider adding a new action instead, but too many variants of an action can get confusing/messy.
Anyway, I've fixed the 1.7.8.4 version for Unity 5.x so it will be in the next update.