query to toString && toLowerCase

@@ -22,7 +22,7 @@ const list = (req, res, next) => {
         cartUrl: helpers.urlFormat('/cart/index/index')
     }, req.query);
     let title = '';
-    let query = req.query.query;
+    let query = (req.query.query || '').toString();
     let isQueryFirstClass = false; // 标识用户搜的是不是一级品类
     let isQuerySecondClass = false; // 标识用户搜的是不是二级品类
     let domain = null;