net: dns: Check interfaces to be NULL before use

Make sure interfaces variable is not NULL before using it.

Coverity-CID: 529857

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

Author: jukkar

subsys/net/lib/dns/resolve.c

@@ -664,7 +664,8 @@ static int dns_resolve_init_locked(struct dns_resolve_context *ctx,
 		char iface_str[IFNAMSIZ] = { 0 };
 		bool found;
 
-		found = is_server_addr_found(ctx, servers_sa[i], interfaces[i]);
+		found = is_server_addr_found(ctx, servers_sa[i],
+					     interfaces == NULL ? 0 : interfaces[i]);
 		if (found) {
 			NET_DBG("Server %s already exists",
 				net_sprint_addr(ctx->servers[i].dns_server.sa_family,