When a gambler tells you he's borrowing money to gamble, he's implicitly warning you that if he loses, repaying the loan might be difficult, and you could end up sharing the loss. As someone with my mindset, I should be cautious and well-informed in such situations.
As long as you don't lend money to someone to gamble, you don't have to be afraid when someone else invites you to gamble with that kind of money. Because the person who has to return the money is the borrower, not you unless you have made a promise to return the money together when you lose at gambling. But if you are only invited and are not told about it by the person who invited you, I think you are free from anything so you don't have to bear paying the money.
I think a lender should have a binding agreement that the borrowers have to sign before they can be granted the loan, so that no matter how the borrower tries to outsmart the lender so that they won't have to repay the loan, the agreement will be presented as evidence before every legal panel. If one lends money to friends and the lender is expected to get the loan repaid, I think they should present strict rules to the borrowers because there are some people who love being debtors. Even if they have the money, such people don't like to pay back their loans. But if the borrower is lending to a best friend or relative and doesn't care if they get repaid or not, then the borrower can just give the loan with strict rules.