That's a sign of irresponsibility, and that person can be a threat to the company, for example if I happen to have a company where we have everything to do with accounting, if I noticed that one of my employees is into gambling he will probably take some stupid risks in the future using money from the company, there are many cases of frauds like this from workers around the world.

I will surely sack him, even if you have a gambling addiction you should avoid gambling at work, you don't know who is watching, go home and fall into your addiction again, not at the office, you are risking your job it seems.