Unset $_GET-variables after action is done

I’ve made a plugin to display a random profile image in my sidebar. In my option panel I’ve made a page where the user can upload a photo and also delete existing images.
The deletion of images sends parameters via $_GET, but after the deletion I’d like to send the user back to the plugin page without the get-variables in the url (this causes an error, since the file is already deleted).

How can I solve this?
I tried with headers, but the admin page sends output before my page is loaded.