Crash in close_or_reextend_intro_circ() (not released)

There is a UAF in:

  if (!TO_CIRCUIT(intro_circ)->marked_for_close) {
    circuit_change_purpose(TO_CIRCUIT(intro_circ),
                           CIRCUIT_PURPOSE_C_INTRODUCE_ACKED);
    circuit_mark_for_close(TO_CIRCUIT(intro_circ), END_CIRC_REASON_FINISHED);
  }
  /* Close the related rendezvous circuit. */
  rend_circ = hs_circuitmap_get_rend_circ_client_side(
                                     intro_circ->hs_ident->rendezvous_cookie);

exact same bug class as #30773 (moved).