Crash on locking Link Annotation

I have opened a pdf file in the viewer with existing link annotations and when I am trying to lock them the app crashes. Please suggest.

may you attach pdf file here?
and share piece of codes that crashed.

The file is attached in the mail.

For locking we are using

int index=0;
page.GetAnnot(index).setLocked(true);

to sure:
1. page object used before Document object closed.
2. page.GetAnnot(index) return not null. mostly need call page.ObjsStart first.
we shall check PDF file too.

Please check the new beta version 3.2beta4 it should fix your annotation lock issue.