fix bug: strip the last message.self
fix bug: strip the last message.self

mukaiu/wechaty,binsee/wechaty,lijiarui/wechaty,wechaty/wechaty,wechaty/wechaty,mukaiu/wechaty,mukaiu/wechaty,wechaty/wechaty,binsee/wechaty,binsee/wechaty,zixia/wechaty,Chatie/wechaty,Chatie/wechaty,lijiarui/wechaty,Chatie/wechaty,zixia/wechaty