Need help, buy script and error .... Purple Haze - Drugs system

Hi ! I have bought this script Purple Haze - Drugs system https://www.gmodstore.com/scripts/view/3792/purple-haze-drugs-system and i have an error, the dev dont help me, ticket, mp : no help ..

I have this error : http://image.noelshack.com/fichiers/2018/19/5/1526001122-capture-d-ecran-2018-05-11-03-07-03.jpg

I dont have modify files ;)

But when the script work : Can i allow only TEAM_GANG for use the dealer ?

Can u help me ?

thx