Check for QUIC in SSL_process_quic_post_handshake

This function doesn't make sense for non-QUIC SSLs.

Change-Id: I3fc08a01f45d8c4e36e449675aecc98ce296abe1
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/73127
Auto-Submit: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Nick Harper <nharper@chromium.org>

ssl/ssl_lib.cc

diff --git a/ssl/ssl_lib.cc b/ssl/ssl_lib.cc
index 5c7693b..82870cd 100644
--- a/ssl/ssl_lib.cc
+++ b/ssl/ssl_lib.cc
@@ -920,7 +920,7 @@
 int SSL_process_quic_post_handshake(SSL *ssl) {
   ssl_reset_error_state(ssl);
 
-  if (SSL_in_init(ssl)) {
+  if (ssl->quic_method == nullptr || SSL_in_init(ssl)) {
     OPENSSL_PUT_ERROR(SSL, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
     return 0;
   }