Can't find anything on urlvoid or urlquery either.
There is an on-line contact form,
http://www.avast.com/contact-form.php?loadStyles for: * Sales inquiries; Technical issues; Website issues; Report false virus alert in file;
Report false virus alert on website; Undetected Malware; Press (Media), issues.
- If you are reporting an FP, then you get another input field open, click Browse button and navigate to the file or enter the web URL for the site you wish to submit for review (Network Shield), etc. A link to this topic also wouldn't hurt.