no banners board sadd fix

db/boards.js

@@ -16,7 +16,9 @@ module.exports = {
 			board = await db.findOne({ '_id': name });
 			if (board) {
 				cache.set(`board_${name}`, board);
-				cache.sadd(`banners_${name}`, board.banners);
+				if (board.banners.length > 0) {
+					cache.sadd(`banners_${name}`, board.banners);
+				}
 			} else {
 				cache.set(`board_${name}`, 'no_exist', 'ex', 3600); //1 hour expiry just so it doesnt grow indefinitely
 			}