cannot display conditions

Hello there,

I have the same problem as Anjxed who posted 6 months ago in this forum, but the solution you provided for him does not work for me; i installed the safecode plugin, pasted your code and just got an error 500, so I had to remove the plugin..

I tried to paste the given code in the function.php file in my child theme, but there is no change at all, I still only get a grey page when I click on conditions.
i dearly need your plugin, may you help ?

thanks