Fix possible use-after-free in lobby server

lobby/LobbyServer.cpp

@@ -325,7 +325,7 @@ void LobbyServer::onDisconnected(const NetworkConnectionPtr & connection, const
 
 	if(activeProxies.count(connection))
 	{
-		const auto & otherConnection = activeProxies.at(connection);
+		const auto otherConnection = activeProxies.at(connection);
 
 		if (otherConnection)
 			otherConnection->close();