return number as file extention name instead of throw a exception
return number as file extention name instead of throw a exception

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