Endless loop in Regex::captures_iter()

[lukaslueg]

AFL found this simple regex that causes Regex::captures_iter() in regex-0.1.71 to enter into an endless loop.

regex::Regex::new("a$").unwrap().captures_iter("a").last()

[BurntSushi]

This appears to be an invalid match bug. Namely, this assert fails:

assert!(Regex::new("a$").unwrap().find_at("a", 1).is_none());