Quicklook在点击导出按钮时崩溃

Question

点击按钮标记的应用程序仅在iOS 7中崩溃并显示以下消息..

 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSCFString rangeOfString:options:range:locale:]: nil argument'
*** First throw call stack:

如何解决这个问题？