UIAlertView+BlocksKit crash

[miku1958]

when use uitextview and try to limit the count of character by reset the text in textViewDidChange method ,crash happen if you type to the max count then shake to undo ,click confirm

crash come to - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex;line 94 [realDelegate alertView:alertView clickedButtonAtIndex:buttonIndex];

error msg is [NSBigMutableString substringWithRange:]: Range {19, 6} out of bounds; string length 19
(null)