[IPV4]: Fix BUG triggered in fib_sync_down()

If you modload then unload a network device,
without creating any ipv4 routes, it is possible
for the laddr hash to be not allocated yet
in fib_semantics.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_semantics.c

@@ -1040,9 +1040,7 @@ int fib_sync_down(u32 local, struct net_device *dev, int force)
 	if (force)
 		scope = -1;
 
-	BUG_ON(!fib_info_laddrhash);
-
-	if (local) {
+	if (local && fib_info_laddrhash) {
 		unsigned int hash = fib_laddr_hashfn(local);
 		struct hlist_head *head = &fib_info_laddrhash[hash];
 		struct hlist_node *node;