From 9464e3fe190818bf6e0ae9dcb56a9020b1f303f7 Mon Sep 17 00:00:00 2001
From: "Roger A. Light" <roger@atchoo.org>
Date: Tue, 20 Nov 2018 10:15:34 +0000
Subject: [PATCH] Guard against possible null client id.

---
 src/persist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/persist.c b/src/persist.c
index b83327c3..3299356d 100644
--- a/src/persist.c
+++ b/src/persist.c
@@ -287,7 +287,7 @@ static int persist__subs_retain_write(struct mosquitto_db *db, FILE *db_fptr, st
 
 	sub = node->subs;
 	while(sub){
-		if(sub->context->clean_session == false){
+		if(sub->context->clean_session == false && sub->context->id){
 			length = htonl(2+strlen(sub->context->id) + 2+strlen(thistopic) + sizeof(uint8_t));
 
 			i16temp = htons(DB_CHUNK_SUB);