Protect against nullptr access during SSL Callback (#6866)

Author: sudheerv

iocore/net/SSLClientUtils.cc

@@ -53,7 +53,7 @@ verify_callback(int signature_ok, X509_STORE_CTX *ctx)
   // No enforcing, go away
   if (netvc == nullptr) {
     // No netvc, very bad.  Go away.  Things are not good.
-    Warning("Netvc gone by in verify_callback");
+    SSLDebug("WARN, Netvc gone by in verify_callback");
     return false;
   } else if (netvc->options.verifyServerPolicy == YamlSNIConfig::Policy::DISABLED) {
     return true; // Tell them that all is well

iocore/net/SSLUtils.cc

@@ -1019,7 +1019,7 @@ ssl_callback_info(const SSL *ssl, int where, int ret)
 
   SSLNetVConnection *netvc = SSLNetVCAccess(ssl);
 
-  if ((where & SSL_CB_ACCEPT_LOOP) && netvc->getSSLHandShakeComplete() == true &&
+  if (netvc && (where & SSL_CB_ACCEPT_LOOP) && netvc->getSSLHandShakeComplete() == true &&
       SSLConfigParams::ssl_allow_client_renegotiation == false) {
     int state = SSL_get_state(ssl);