Fatal error when using Force the user to choose a term from a deepest level

When I choose "Force the user to choose a term from a deepest level" and submit the form I get a server 500 error (probably out of memory or something)
when i refresh the settings page I get the following messages from drupal. Btw, this only happens with content taxonomy HS, not taxonomy HS

* warning: Missing argument 1 for drupal_retrieve_form() in /path/site.com/includes/form.inc on line 179.
* warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, '' was given in /hpath/site.com/includes/form.inc on line 218.
* warning: uasort() [function.uasort]: The argument should be an array in /path/site.com/includes/common.inc on line 2148.