Adversary chain may crash if potion is used towards the end of a foe battle

[cosk]

This does not happen every time, but Aurors see it often enough because many try to use an exstimulo just before the end of a foe to work around issue #8.

I theorize that this has the same root cause as #7. Client and server get out of sync. Client thinks that the foe is dead, server thinks that the foe is still kicking (or the other way around).

Workaround: skip a turn after using a potion.