The person meant absolutely nothing! I know a few of such people. They stick their hands into their pocket, grab a handful of words, and toss it — before running off and forgetting about the whole incident. The person enjoys the feeling of saying, “Be happy”. That’s all there is to it. When I hear that kind of talk, I just smile back as if he said something worthy of a half smile, and move on.
Think of it as the verbal equivalent to a wack on the back accompanied by, “Haya doin!?”