Send 404 if applink icon does not exist

src/routes/applinks.js

@@ -84,6 +84,7 @@ async function getIcon(req, res, next) {
 
     const [error, icon] = await safe(applinks.getIcon(req.params.id, { original: req.query.original }));
     if (error) return next(BoxError.toHttpError(error));
+    if (!icon) return next(new HttpError(404, 'no such icon'));
 
     res.send(icon);
 }