After $_GET['q'] is better rewritten dynamically

Hi, in my site I displayed the message list in a block, I include'privatemsg.pages' as the content of the block, which means the url of this block page is not something like 'messages/xx', but 'node/xxx'.
The pager is generated with the $_GET['q'], and it's correct (with url 'node/xxx')
The issue is that when I choose an action 'Mark as read' or 'Mark as unread', the $_GET['q'] is directly rewritten to 'messages/xx', so the pager is no longer correct.
Therefore I'm thinking shall we set the $_GET['q'] to something dynamic, like '$_SERVER["HTTP_REFERER"]'
The 'undo' function also come with this issue.
Here is a patch I wrote, is that OK? It works on my site, but I'm not sure I'll cause other issues in different situation.
Thanks!