netfilter: nf_tables: check for NULL in nf_tables_newchain pcpu stats allocation

alloc_percpu returns NULL on failure, not a negative error code.

Fixes: ff3cd7b3 ("netfilter: nf_tables: refactor chain statistic routines")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -1328,10 +1328,10 @@ static int nf_tables_newchain(struct sock *nlsk, struct sk_buff *skb,
 			basechain->stats = stats;
 		} else {
 			stats = netdev_alloc_pcpu_stats(struct nft_stats);
-			if (IS_ERR(stats)) {
+			if (stats == NULL) {
 				module_put(type->owner);
 				kfree(basechain);
-				return PTR_ERR(stats);
+				return -ENOMEM;
 			}
 			rcu_assign_pointer(basechain->stats, stats);
 		}