mrb_class_new(mrb_state *mrb, struct RClass *super)
{
  struct RClass *c;

  if (super) {
    mrb_check_inheritable(mrb, super);
  }
  c = boot_defclass(mrb, super);
  if (super) {
    MRB_SET_INSTANCE_TT(c, MRB_INSTANCE_TT(super));
  }
  make_metaclass(mrb, c);

  return c;
}

The product dereferences a pointer that it expects to be valid but is NULL.