Avoid re-assigning zero to `ret` variable.
Resolve #3182.

Signed-off-by: irwir <irwir@users.noreply.github.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index dbc5a3e..ccfc4bd 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2747,9 +2747,7 @@
     {
         ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_MISSING;
 
-        if( authmode == MBEDTLS_SSL_VERIFY_OPTIONAL )
-            ret = 0;
-        else
+        if( authmode != MBEDTLS_SSL_VERIFY_OPTIONAL )
             ret = MBEDTLS_ERR_SSL_NO_CLIENT_CERTIFICATE;
 
         goto exit;