I applied for a Web developer job in Quebec City, and they called me back for a phone interview. Everything went well, it last for over a hours, and at the end they ask me to send code simple and a portfolio, but in my research about the company and their products I found a PHP error(bug) in their app.

Should I tell them or I would that make me look like a total jerk and blow my chance for a interview? I know it might sound stupid. As a junior developer I did 2 interviews they didn't go so well. I am very interested in this position part of my question is like a big lack of confidence so to make it short should I tell them about where is the error and how to fix it?

Thanks