This question already has an answer here:
I came across this oddity when I ran this search query, sorted by votes:
That question has zero answers, but its search result summary is formatted as though it has an accepted answer (green box, yellow-highlighted text). In fact, the CSS class on that div is
Skynet Exchange Stack Exchange system has become so intelligent, that it knows the OP solved their own problem (answering it in the question portion of the post), and thus it's marked as "answered-accepted."
Or maybe, after over 5 years, the question has just accepted the fact that it isn't going to get any answers.
Regardless, this seems like a display bug =)