uncaught exception: "redeclaration of const document" in components/greasemonkey.js, line 302

Steps to reproduce:

1. Open a page and let Greasemonkey inject some scripts
2. Open a sidebar (for example your history or bookmarks)
3. Close that sidebar again

Build identifier:Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101027 Firefox/3.6.12
Couldn't reproduce this with FF4 nightly.