Fix hang on markdown empty string

utility.js

@@ -81,14 +81,12 @@ module.exports = {
       } else {
         let res = obj, cnt = keys.length;
         for (let key of keys) {
-          if (res[key].trim()) {
           renderer(res[key], (s) => {
             res[key] = replaceUI(s);
             if (!--cnt) resolve(res);
           });
         }
       }
-      }
     });
   },
   formatDate(ts, format) {