A null pointer indicates that there is "nothing there" - it points at nothing. So you can't delete or free it, because you didn't assign it.
Most likely, this is an error message you are getting as a result of a problem in your code - you are trying to use a pointer that you have not assigned an address into, so the system is reporting a "null pointer" error.
Something like this:
int x = 77;
x = x + *p;
Use the debugger: put a breakpoint on the first line of the function that shows the error and step through your code, looking at the variables and exactly what is going on. It should be fairly obvious what is causing the problem.
We can't do that for you: we can't see your screen, access your HDD, or read your mind! :laugh: