pset5 unload segmentation fault

Question

I am getting seg fault. I am not being able to determine error by debugger.

 bool unload(wordtree* del)
{
if(del==NULL)
return true;

for(int i=0;i<27;i++)
{
    if(del->ptr[i]!=NULL)
    {
        del = del->ptr[i];
        unload(del);
    }
}
free(del);

  return true;
}