netfilter: nf_tables: always initialize flowtable hook list in transaction

The hook list is used if nft_trans_flowtable_update(trans) == true. However,
initialize this list for other cases for safety reasons.

Fixes: 78d9f48f ("netfilter: nf_tables: add devices to existing flowtable")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -544,6 +544,7 @@ static int nft_trans_flowtable_add(struct nft_ctx *ctx, int msg_type,
 	if (msg_type == NFT_MSG_NEWFLOWTABLE)
 		nft_activate_next(ctx->net, flowtable);
 
+	INIT_LIST_HEAD(&nft_trans_flowtable_hooks(trans));
 	nft_trans_flowtable(trans) = flowtable;
 	nft_trans_commit_list_add_tail(ctx->net, trans);