[openssl/openssl] 635494: ec_kmgmt.c: check the return of BN_CTX_get() in time.

[Jerry]

  Branch: refs/heads/openssl-3.1
  Home:   https://github.com/openssl/openssl
  Commit: 63549494c8912aecbb382b7250179b2265b9bd83
      https://github.com/openssl/openssl/commit/63549494c8912aecbb382b7250179b2265b9bd83
  Author: xkernel <xkernel.wang at foxmail.com>
  Date:   2022-12-22 (Thu, 22 Dec 2022)

  Changed paths:
    M providers/implementations/keymgmt/ec_kmgmt.c

  Log Message:
  -----------
  ec_kmgmt.c: check the return of BN_CTX_get() in time.

If x and y are all NULL, then it is unnecessary to do subsequent operations.

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/19905)

(cherry picked from commit 467b0492c1e597857b30b91ed72605387aa9825b)