Call to undefined function trace_hook() (2)

When I try to view an unexisting page address with / at the end (like www.mysite.com/drupal/nonexistingpage/ ), Trace is crashing and giving the error message "Fatal error: Call to undefined function trace_hook() in C:\Project\drupal\sites\all\modules\trace\trace.module on line 124". It should give a 404 error. There is no problem, when the address does not have / at the end (like www.mysite.com/drupal/nonexistingpage ). Page gives 404 error as expected.