empty queue prints for me value

i created an object from struct then pushed into queue then pop it after that i print what inside it printed for me salary how that comes the queue should be empty i also tried to replace .salary with the other variables it gives me their values.

#include <iostream>
#include <queue>
using namespace std;

struct employee {
    string name;
    int age;
    int salary;
};

int main() {

    queue<employee> q;
    employee e {"Rio",22,1000};

    q.push(e);

    q.pop();
    cout<<q.back().salary<<endl;

    return 0;
}

i tried to push an object named employee to queue then i pop it from the queue then i used .back() function and it gives me value while the queue is empty

If the queue is empty, then calling .back() on it has undefined behavior. Any behavior of the program is valid and no specific behavior can be expected.