What's the error in this code?

let john = true;
let thor = 'asgard';
let falcon = 1001;
let ghost;
console.log('john: ' + typeof john);
console.log('thor: ' + typeof thor);
console.log('falcon: ' + typeof falcon);
console.log('ghost: ' + typeof ghost);

i solved the code but showing error that you forget to log the typeof variable "ghost" on console.