White screen bulk action but no selected comments

[duck_]

1. Visit wp-admin/edit-comments.php
2. Perform a bulk action without checking any comments
3. White screen

The problem is that wp_get_refere() is returning false (since _wp_http_referer == REQUEST_URI) and so the ​redirect on line 33 does nothing then we exit.

Pre-3.1 there was no exit call after the redirect so it just fell through and ​redirected at the end of the bulk action block where $redirect_to is set because add_query_arg (called by remove_query_arg) uses $_SERVER['REQUEST_URI'] when the old query is false.

[scribu]

(In [16580]) Prevent WSOD when no comments selected for bulk action. See #15572