Hi Micky,
This fix was done a very long time ago (https://github.com/PukunuiAustralia/moodle-mod_certificate/commit/715839cc80c7c4507c8cf7f32b50aff56370ddc3 ) in the latest certificate code. If you had to manually do the change yourself I suspect you are using an old version (unless you are using 1.9 which I have not updated).
Regards, Mark