[Pharo-project] Pharo 2.0-20245 | Group creation

Hi, Group creation raises a DNU. Replacing messages -GroupAnnouncer announcer by -GroupAnnouncer uniqueInstance seems to solve the problem, though I'm not sure if this is correct. Noury -- http://twitter.com/#!/NouryBouraqadi http://www.kroobe.com/profile/noury