Is this a common expression in German? In a practical sense, if you were to actually say this, would you mean "In general I do not have desires; I am an emotionally vacant robot" or is it it like, if someone asks you what you want to do this weekend, and you shrug "Ich habe keine Wünsche", to mean "I don't really mind"?
I don't think this is common in German. The closest you would get is the obligatory 'Haben Sie sonst noch einen Wunsch?' at your local bakery. But that rather means 'Do you want anything else/additional?'. One might also be 'wunschlos glücklich', perfectly happy. I guess, this sentence is just a bad, random example after all. If you took it literally and asked for my personal opinion, I would say it could either mean, you have no more desires or wishes above your quite good life or you really stopped wishing or hoping or dreaming, since you have always been disappointed whenever you did.