[Greasemonkey] Aborting script on bad reference

[Torsten vom Vaterland]

I wanted to port the anti-autocomplete-blocker bookmarklet to
greasemonkey and it's choking.

Here's the code:
http://sourcepost.sytes.net/sourcepost/sourceview.aspx?source_id=27699

It seems to choke when it doesnt find onsubmit anywhere, and aborts the script.

Any hints?