test/crypto: fix null check for ZUC authentication

[ upstream commit e6d37ff ]

Check if the returned op is NULL because of failure,
before using it and causing a segmentation fault.

Fixes: 4c99481 ("app/test: add ZUC")

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>

app/test/test_cryptodev.c

@@ -6233,8 +6233,8 @@ test_zuc_authentication(const struct wireless_test_data *tdata)
 	else
 		ut_params->op = process_crypto_request(ts_params->valid_devs[0],
 				ut_params->op);
-	ut_params->obuf = ut_params->op->sym->m_src;
 	TEST_ASSERT_NOT_NULL(ut_params->op, "failed to retrieve obuf");
+	ut_params->obuf = ut_params->op->sym->m_src;
 	ut_params->digest = rte_pktmbuf_mtod(ut_params->obuf, uint8_t *)
 			+ plaintext_pad_len;