MT#55283 safeguard against Redis connect failure

Avoids segfault is extra connection can't be established

Closes #1903

Change-Id: I6eb7315f6774015703c7ad036e08596f7f550d60
(cherry picked from commit 172f389395)

daemon/redis.c

@@ -2316,9 +2316,14 @@ int redis_restore(struct redis *r, bool foreign, int db) {
 	mutex_init(&ctx.r_m);
 	g_queue_init(&ctx.r_q);
 	ctx.foreign = foreign;
-	for (int i = 0; i < rtpe_config.redis_num_threads; i++)
-		g_queue_push_tail(&ctx.r_q,
-				redis_dup(r, db));
+	for (int i = 0; i < rtpe_config.redis_num_threads; i++) {
+		struct redis *dup = redis_dup(r, db);
+		if (!dup) {
+			rlog(LOG_ERR, "Failed to create thread connection to Redis");
+			goto err;
+		}
+		g_queue_push_tail(&ctx.r_q, dup);
+	}
 	gtp = g_thread_pool_new(restore_thread, &ctx, rtpe_config.redis_num_threads, TRUE, NULL);
 
 	for (int i = 0; i < calls->elements; i++) {