apps/s_client.c: add missing null check
apps/s_server.c: remove unnecessary null check

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4558)

apps/s_client.c

diff --git a/apps/s_client.c b/apps/s_client.c
index 96bfc15..019e735 100644
--- a/apps/s_client.c
+++ b/apps/s_client.c
@@ -1866,6 +1866,9 @@
         goto end;
 
     con = SSL_new(ctx);
+    if (con == NULL)
+        goto end;
+
     if (sess_in != NULL) {
         SSL_SESSION *sess;
         BIO *stmp = BIO_new_file(sess_in, "r");