It will still not lose, since it'd be as if the double spent ones had never happened. They do stop winning, but never lose
The casino will lose money in the long term.
In any casino, some people win and some people lose. The casino get money from losers and give it to winners.
If a significant number of losers cheat the casino with double-spending, the money that casino must pay to winners will be lower than the money they get from losers and the casino lose money.
Assuming all losers cheat the casino with invalidating their deposits, it's like that all gamblers win money and there is no loser.