Simplify SSL_get0_next_proto_negotiated.

The pointer and length fields should always be kept in sync. Other code
already assumes this anyway.

Change-Id: I62bc77b805cd4d81f2caa4aa49ad3e9d96faa25e
Reviewed-on: https://boringssl-review.googlesource.com/17306
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

ssl/ssl_lib.c

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 3b951e0..1b002a5 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -1714,11 +1714,7 @@
 void SSL_get0_next_proto_negotiated(const SSL *ssl, const uint8_t **out_data,
                                     unsigned *out_len) {
   *out_data = ssl->s3->next_proto_negotiated;
-  if (*out_data == NULL) {
-    *out_len = 0;
-  } else {
-    *out_len = ssl->s3->next_proto_negotiated_len;
-  }
+  *out_len = ssl->s3->next_proto_negotiated_len;
 }
 
 void SSL_CTX_set_next_protos_advertised_cb(