[openssl/openssl] ce0a7c: Coverity 1516624: Fix overrun memory access.

[Pauli]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: ce0a7cadadb973216399e70d3a69f352b0843deb
      https://github.com/openssl/openssl/commit/ce0a7cadadb973216399e70d3a69f352b0843deb
  Author: Pauli <pauli at openssl.org>
  Date:   2022-11-03 (Thu, 03 Nov 2022)

  Changed paths:
    M test/punycode_test.c

  Log Message:
  -----------
  Coverity 1516624: Fix overrun memory access.

Not possible to hit but good to address.

Reviewed-by: Hugo Landau <hlandau at openssl.org>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19576)