get audio/image/video file base64 right (#1314)
get audio/image/video file base64 right (#1314)

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