[IPV4]: Do not try to unhash null-netdev nexthops.

Signed-off-by: Christian Ehrhardt <ehrhardt@mathematik.uni-ulm.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_semantics.c

@@ -163,6 +163,8 @@ void fib_release_info(struct fib_info *fi)
 		if (fi->fib_prefsrc)
 			hlist_del(&fi->fib_lhash);
 		change_nexthops(fi) {
+			if (!nh->nh_dev)
+				continue;
 			hlist_del(&nh->nh_hash);
 		} endfor_nexthops(fi)
 		fi->fib_dead = 1;