Mafia: Fix rare bug

A bug so rare that it took a theme as complex as Shop to find it.
Basically, if 2 players have the same role and one of them use a night action which can end converting the other (convert/massconvert/onDeath), the converted player may get weird results if they tried to use the same action.
Merge pull request #807 from IceKirby/patch-34

Mafia: Fix rare bug