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);
 }