netfilter: nf_tables: selective rule dump needs table to be specified

Table needs to be specified for selective rule dumps per chain.

Fixes: 241faece ("netfilter: nf_tables: Speed up selective rule dumps")
Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -2350,7 +2350,7 @@ static int nf_tables_dump_rules(struct sk_buff *skb,
 		if (ctx && ctx->table && strcmp(ctx->table, table->name) != 0)
 			continue;
 
-		if (ctx && ctx->chain) {
+		if (ctx && ctx->table && ctx->chain) {
 			struct rhlist_head *list, *tmp;
 
 			list = rhltable_lookup(&table->chains_ht, ctx->chain,