sanity checks; server crash fix

cockatrice/src/cardzone.cpp

@@ -99,6 +99,10 @@ void CardZone::addCard(CardItem *card, bool reorganize, int x, int y)
 CardItem *CardZone::getCard(int cardId, const QString &cardName)
 {
 	CardItem *c = cards.findCard(cardId, false);
+	if (!c) {
+		qDebug() << "CardZone::getCard: card id=" << cardId << "not found";
+		return 0;
+	}
 	// If the card's id is -1, this zone is invisible,
 	// so we need to give the card an id and a name as it comes out.
 	// It can be assumed that in an invisible zone, all cards are equal.

cockatrice/src/player.cpp

@@ -563,6 +563,10 @@ void Player::eventSetCardAttr(Event_SetCardAttr *event)
 			emit logSetTapped(this, QString("-1"), event->getAttrValue() == "1");
 	} else {
 		CardItem *card = zone->getCard(event->getCardId(), QString());
+		if (!card) {
+			qDebug() << "Player::eventSetCardAttr: card id=" << event->getCardId() << "not found";
+			return;
+		}
 		setCardAttrHelper(card, event->getAttrName(), event->getAttrValue(), false);
 	}
 }

common/server.cpp

@@ -65,8 +65,7 @@ void Server::closeOldSession(const QString &playerName)
 		}
 	if (session) {
 		qDebug() << "found";
-		removeClient(session);
+		delete session; // ~Server_ProtocolHandler() will call Server::removeClient
-		delete session;
 	}
 }