[php-src] PR #23339: ext/ldap: fix crash in ldap_exop_sync() when $response_data is omitted

Pull Request: https://github.com/php/php-src/pull/23339 Author: lacatoire ldap_exop_sync() passes force_sync = true to php_ldap_exop(), so the block that writes back $response_data is always entered regardless of whether the argument was supplied. When it is omitted, retdata is NULL, and both ZEND_TRY_ASSIGN_REF_STRINGL and ZEND_TRY_ASSIGN_REF_EMPTY_STRING dereference it — ZEND_ASSERT(Z_ISREF_P(zv)) in debug builds, a NULL dereference crash in release. ldap_exop() is not affected: there retdata != NULL is what selects the branch in the first place. The fix mirrors the existing if (retoid) guard a few lines above. ldap_memfree() is still called unconditionally so there is no memory leak. ```php ldap_exop_sync($ld, LDAP_EXOP_WHO_AM_I); // segfault before, bool(true) after ``` Reproduced on PHP 8.4.22 (exit code 139). Present since ldap_exop_sync() was introduced in PHP 8.3.0.