Hyperlinks destination seems empty

We receive pdfs with hyperlinks pointing to a destination page. When trying to extract the destination however, we always get a null reference.
Attached is a small example pdf. Page 8 contains a hyperlink/annotation on the page that references page 3.
We succeed to get the annotation and to get the text from the annotation but not the destination.
Could you help us to get the page number from these kind of hyperlinks/annotations?

Thanks in advance for your help!

Kay Geens