netfilter: xt_hashlimit: dl_seq_stop() fix

If dl_seq_start() memory allocation fails, we crash later in
dl_seq_stop(), trying to kfree(ERR_PTR(-ENOMEM))

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 9e9c489..70d561a 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -879,7 +879,8 @@
 	struct xt_hashlimit_htable *htable = s->private;
 	unsigned int *bucket = (unsigned int *)v;
 
-	kfree(bucket);
+	if (!IS_ERR(bucket))
+		kfree(bucket);
 	spin_unlock_bh(&htable->lock);
 }