exc_bad_access,while canlel input

It not always happen ,but in some inputfield , detail step is below if I not type any words , click cancel its ok .it would crash when i click canel after I type some words ,in the xcode it stop in setText method , multiline is NO , in else block , exc_bad_access , And unity version is 5.01f ,xcode version 6.3 , is any one happened this situation , please tell some word ,and thks much.