fix expire time.

@@ -48,9 +48,9 @@ passport.use(new LocalStrategy({
         return done({message: '登录账号格式错误'}, null);
     }
 
-    let expire = req.cookies['LE' + md5('_LOGIN_EXPIRE')];
+    let expire = req.cookies['LE' + md5('_LOGIN_EXPIRE')] || '';
 
-    if (_.isEmpty(expire) || expire < (new Date()).getTime() / 1000) {
+    if (expire && expire < (new Date()).getTime() / 1000) {
         return done({message: '页面停留时间过长，请刷新页面'}, null);
     }