robots.txt missing when Event Calendar 3.2.beta2 is active

With Event Calendar 3.2.beta2 running on WordPress 2.8.4, the dynamic robots.txt is not generated. When visiting http://mydomain.tld/robots.txt one normally gets a white page containing only

User-agent: *
Disallow:

But when Event Calendar 3.2.beta2 is active, that request results in a 404 Not Found page.

http://wordpress.org/extend/plugins/event-calendar/