lightningd: allow outgoing_scid without outgoing amount.

This (will) happen if they ask is to forward to an unknown scid.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/peer_htlcs.c

@@ -2765,7 +2765,7 @@ void json_format_forwarding_object(struct json_stream *response,
 				    "in_msatoshi", "in_msat");
 
 	/* These can be unset (aka zero) if we failed before channel lookup */
-	if (cur->channel_out.u64 != 0) {
+	if (!amount_msat_eq(cur->msat_out, AMOUNT_MSAT(0))) {
 		json_add_amount_msat_compat(response,
 					    cur->msat_out,
 					    "out_msatoshi",  "out_msat");