f sanity check the doc claim

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -5504,8 +5504,11 @@ impl<Signer: Sign> Channel<Signer> {
 	pub fn queue_add_htlc<L: Deref>(&mut self, amount_msat: u64, payment_hash: PaymentHash, cltv_expiry: u32, source: HTLCSource,
 		onion_routing_packet: msgs::OnionPacket, logger: &L)
 	-> Result<(), ChannelError> where L::Target: Logger {
-		self.send_htlc(amount_msat, payment_hash, cltv_expiry, source, onion_routing_packet, true, logger)
-			.map(|msg_opt| assert!(msg_opt.is_none(), "We forced holding cell?"))
+		let res = self
+			.send_htlc(amount_msat, payment_hash, cltv_expiry, source, onion_routing_packet, true, logger)
+			.map(|msg_opt| assert!(msg_opt.is_none(), "We forced holding cell?"));
+		if let Err(e) = &res { if let ChannelError::Ignore(_) = e {} else { debug_assert!(false, "Queueing cannot trigger channel failure"); } }
+		res
 	}
 
 	/// Adds a pending outbound HTLC to this channel, note that you probably want