调整定时任务，去除无效发送内容

robot.py

@@ -706,8 +706,9 @@ class Robot:
 
             for r in receivers:
                 if self.gbm.get_group_permission(r, Feature.DAILY_SUMMARY) == PermissionStatus.ENABLED:
-                    output = await self.message_storage.generate_and_send_ranking(r, self.allContacts)
-                    await self.ipad_bot.send_text_message(r, output)
+                    tag, output = await self.message_storage.generate_and_send_ranking(r, self.allContacts)
+                    if tag:
+                        await self.ipad_bot.send_text_message(r, output)
         except Exception as e:
             self.LOG.error(f"SendRanking error：{e}")