Deleting a char array

This question is related to this one. Given this code:

char *p = new char[200];
delete[] p;

what would happen if you set p[100] = '\0' before deleting p?

I had some code where I got a debug error when I tried to delete a not null-terminated char array, something about deleting heap memory that's not assigned. It seemed to delete memory out of the array's bounds.