When some user try to send request membership to closed group, 

owner of the group getting an email with following text:

'...or click below to view the group's join requests:

http://www.domain.com/mod/groups/membershipreq.php?group_guid=[group_guid] 

And after clicking on this link the dashboard page opens. 

It happens because true link for 1.8 should be like this

http://www.domain.com/groups/requests/[group_guid]