using tablesort clears issue queue filters

doing cvs archeology on a weird part of issue.inc that's causing other problems in http://drupal.org/node/57023, i discovered that in revision 1.21 (2003-10-05), kjartan apparently fixed a bug that has since resurfaced. i can't find any issue # for the original bug, so i'm submitting a new one. ;)

to reproduce:

1. goto a project's issue page, e.g., http://drupal.org/project/issues/project_issue
2. select something to filter the view with based on the drop-down menus (e.g. status: "active") and hit submit -- you only see active issues (so far, so good).
3. select something else to filter the view with based on the drop-down menus (e.g. category: "bug reports") and hit submit -- you only see active bug reports (so far, still good).
4. click on "Pri" to sort by priority. now, you see all issue categories in all of the default states again, not just the active bugs. :(

something is seriously wrong with the interaction of args being added to the URL by the tablesort code, and the code trying to generate the right query based on the form elements.