MUID Error

I have small ERROR problem

"ItemSystems_Database:307: attempt to index a nil value (local 'itemMUID')"

muid = itemMUID:match("^(.+):"),

PLEASE . Help me

Replicating the error, it just looks like itemMUID is nil

local itemMUID = nil
muid = itemMUID:dargl() --> attempt to index a nil value (local 'itemMUID')