Only reactivate player if it exists in the current game.

src/net/common/servergamestate.cpp

@@ -1314,8 +1314,10 @@ ServerGameStateHand::ReactivatePlayers(boost::shared_ptr<ServerGame> server)
 	PlayerIdList::iterator end = reactivateIdList.end();
 	while (i != end) {
 		boost::shared_ptr<PlayerInterface> tmpPlayer(server->GetGame().getPlayerByUniqueId(*i));
+		if (tmpPlayer) {
 			tmpPlayer->markRemoteAction();
 			tmpPlayer->setIsSessionActive(true);
+		}
 		++i;
 	}
 }