display error e all

I have display errors E_ALL in my server (i think its better)

But in throw an error about the $slug variable in include/public.php line 29

I tried to figure out whats happening in there to suggest a change but i finished “avoiding the mess” using:

self::$_instance = new self (@$slug);

I really dont know where is defined that variable (in fact, nowhere, that’s the warning)

https://ww.wp.xz.cn/plugins/official-add-to-homescreen/