My personal understanding at this point in time is this: You looked at another person’s code to fix an issue with their own game. You they didn’t nick an entire mechanic but rather looked at how a rather basic mechanic worked elsewhere and made corrections to their own code based on that knowledge. You just chose to do so by looking at a finished project rather than a tutorial.
If my understanding of that part of… the current situation is correct I think you’re fine - legally and morally. If it was a bit more than that or maybe you just want to thank the person whose publicly available code helped you on a early step of your career, just contact that games developer, explain how their code helped you with your free project and ask them if they want to be credited and how. Most game developers are pretty cool, passionate people. :) They will probably be happy to hear that their work helped you. (Just don’t bother them with… The other stuff that’s going on in this thread.)