Is it safe to delete a pointer to nullptr

I did a test on a online compiler(online compiler) with the below code.

#include <iostream>

using namespace std;

int main()
{
    int * a = nullptr;
    delete a;
    return 0;
}

The program compiles and runs with no problem. So it is safe to delete pointer too a nullptr. However, you can not execute delete nullptr; directly since nullptr is a pointer literal.