[openssl/openssl] fbeb48: Coverity: explicit null dereference

[Pauli]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: fbeb4866f4250a4a23e7afb884a0aa0456d152f8
      https://github.com/openssl/openssl/commit/fbeb4866f4250a4a23e7afb884a0aa0456d152f8
  Author: Pauli <pauli at openssl.org>
  Date:   2022-09-07 (Wed, 07 Sep 2022)

  Changed paths:
    M test/list_test.c

  Log Message:
  -----------
  Coverity: explicit null dereference

Coverity is being pretty silly here but adding the explicit pointer checks
will stop a crash if something goes badly awry.

Fixes Coverity 1513706 - 1513709

Reviewed-by: Shane Lontis <shane.lontis at oracle.com>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19136)