What's next for the salad chain after another dismal earnings report?Sweetgreen (SG +2.68%) may be on its way to having one of the worst years in restaurant stock history. Year to date through Nov. 10, shares of the fast-casual salad chain are down 83% for the year, and down 88% from its peak last November. It's unusual for a restaurant stock to suffer such a rapid decline, especially when there isn't an obvious culprit. There hasn't been a crushing recession or a blunder like Chipotle's E. coli crisis back ...