net: ipmr: ipmr_get_table() returns NULL

The ipmr_get_table() function doesn't return error pointers it returns
NULL on error.

Fixes: 4f75ba69 ("net: ipmr: Add ipmr_rtm_getroute")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipmr.c

@@ -2431,8 +2431,8 @@ static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 	tableid = tb[RTA_TABLE] ? nla_get_u32(tb[RTA_TABLE]) : 0;
 
 	mrt = ipmr_get_table(net, tableid ? tableid : RT_TABLE_DEFAULT);
-	if (IS_ERR(mrt)) {
-		err = PTR_ERR(mrt);
+	if (!mrt) {
+		err = -ENOENT;
 		goto errout_free;
 	}