Fix a crash in SSLfatal due to invalid enc_write_ctx

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5645)

ssl/statem/statem.c

diff --git a/ssl/statem/statem.c b/ssl/statem/statem.c
index a574853..1f221e7 100644
--- a/ssl/statem/statem.c
+++ b/ssl/statem/statem.c
@@ -123,7 +123,7 @@
     s->statem.in_init = 1;
     s->statem.state = MSG_FLOW_ERROR;
     ERR_put_error(ERR_LIB_SSL, func, reason, file, line);
-    if (al != SSL_AD_NO_ALERT)
+    if (al != SSL_AD_NO_ALERT && !s->statem.invalid_enc_write_ctx)
         ssl3_send_alert(s, SSL3_AL_FATAL, al);
 }
 

ssl/statem/statem.h

diff --git a/ssl/statem/statem.h b/ssl/statem/statem.h
index 1935718..95dd881 100644
--- a/ssl/statem/statem.h
+++ b/ssl/statem/statem.h
@@ -100,6 +100,7 @@
     /* Should we skip the CertificateVerify message? */
     unsigned int no_cert_verify;
     int use_timer;
+    int invalid_enc_write_ctx;
 };
 typedef struct ossl_statem_st OSSL_STATEM;