stack: Do not add error if pop/shift/value accesses outside of the stack

stack: Do not add error if pop/shift/value accesses outside of the stack

This partially reverts commit 30eba7f35983a917f1007bce45040c0af3442e42.
This is legitimate use of the stack functions and no error
should be reported apart from the NULL return value.

Fixes #19389

Reviewed-by: Todd Short <todd.short@me.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19400)