Teaser link "Upgrade to Pro site" does not show up when option for free forums is set to 0

Hey guys,
I have trouble with the Forum plugin in combination with Pro Sites.
When I set the option Maximum number of forums for the free user level in Network Admin > Options > Forums to 0 (zero), free user blogs still get a link Click here to add a new forum. When I click the link only an empty page opens inside the dashboard.
But I think it should show a teaser link to the checkout page likeTo use the Forum, please upgrade to Pro ».
Same happens if I set the option to 1 free forum. I can create one free forum and if I want to add a second forum the link Click here to add a new forum appears again, but it goes nowhere.

Also, there is an option inside forums.php
define('FORUM_DEMO_FOR_NON_SUPPORTER', false);
should I change it to true in order to get a teaser ad for non pro users?
Thanks
Robert