Before “Seinfeld” and “Curb Your Enthusiasm,” there was “Prognosis: Negative,” a film script written by Larry David in the 1980s that was never produced. Thanks to a Reddit user from Rochester, N.Y., a 1983 draft of the screenplay has been uploaded to the internet. (Read a PDF here .) The 24-year-old, named Jeremy Smith, bought the script on eBay from a seller offering unpublished scripts; it’s unclear how “Prognosis: Negative” was obtained in the first place. The existence of “Prognosis: Negative” has long been known (its title was a recurring joke in “Seinfeld”), but the screenplay had never been available to read until now. Popular on Variety “Prognosis: Negative” follows a man named Leo Black, who is incapable of committing to women. When he discovers an ex-girlfriend is dying, he decides to rekindle their relationship. After all, she won’t be around for much longer.…