Navigation error

I’ve just updated to 1.0.2 but the same error occurred in 1.0.1 too – 1.0.2 appeared while I was writing this message! On pages 1-4 of guestbook entries the navigation links work fine but an error occurs when you reach page 5 and above. The link to page 1 is:

http://mysite.org/&pageNum=1 (this is wrong and brings up a 404 error)

instead of

http://mysite.org/visitors/&pageNum=1 (this would be the correct link).

This error only affect the link to page 1. I have looked at the code in page-entries.php but can’t see what, if anything, might be wrong.

https://ww.wp.xz.cn/plugins/gwolle-gb/