上传ipa到AppStore报错ERROR ITMS-90023

上传ipa到AppStore报错
ERROR ITMS-90023: “Missing required icon file. The bundle does not contain an app icon for iPad of exactly ‘76x76’ pixels, in .png format for iOS versions >= 7.0.”
An unknown error occurred.

提示缺少76像素的icon，可是在设置icon的地方没有设置76像素的框

解决办法：
自己创建一个icon目录