ssl test ssl_decrypt_non_etm_cbc(): add missing ret check

Signed-off-by: Przemyslaw Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index 4635b65..1d63702 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -3592,6 +3592,8 @@
                                    MBEDTLS_SSL_MINOR_VERSION_3,
                                    0 , 0 );
 
+    TEST_ASSERT( ret == 0 );
+
     /* Determine padding/plaintext length */
     TEST_ASSERT( length_selector >= -2 && length_selector <= 255 );
     block_size = t0.ivlen;