Fix reachable unwrap on non-channel_type manual channel acceptance

If we receive an `OpenChannel` message without a `channel_type`
with `manually_accept_inbound_channels` set, we will `unwrap()`
`None`.

This is uncommon these days as most nodes support `channel_type`,
but sadly is rather trivial for a peer to hit for those with manual
channel acceptance enabled.

Reported in and fixes lightningdevkit#2804. Luckily, the updated
`full_stack_target` has no issue reaching this issue quickly.

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -6845,6 +6845,16 @@ pub(super) struct InboundV1Channel<SP: Deref> where SP::Target: SignerProvider {
 	pub unfunded_context: UnfundedChannelContext,
 }
 
+/// Fetches the [`ChannelTypeFeatures`] that will be used for a channel built from a given
+/// [`msgs::OpenChannel`].
+pub(super) fn channel_type_from_open_channel(msg: &msgs::OpenChannel) -> ChannelTypeFeatures {
+	if let Some(features) = &msg.channel_type {
+		features.clone()
+	} else {
+		ChannelTypeFeatures::only_static_remote_key()
+	}
+}
+
 impl<SP: Deref> InboundV1Channel<SP> where SP::Target: SignerProvider {
 	/// Creates a new channel from a remote sides' request for one.
 	/// Assumes chain_hash has already been checked and corresponds with what we expect!
@@ -6884,7 +6894,7 @@ impl<SP: Deref> InboundV1Channel<SP> where SP::Target: SignerProvider {
 			channel_type.clone()
 		} else {
 			let channel_type = ChannelTypeFeatures::from_init(&their_features);
-			if channel_type != ChannelTypeFeatures::only_static_remote_key() {
+			if channel_type != channel_type_from_open_channel(msg) {
 				return Err(ChannelError::Close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
 			}
 			channel_type

lightning/src/ln/channelmanager.rs

@@ -43,7 +43,7 @@ use crate::events::{Event, EventHandler, EventsProvider, MessageSendEvent, Messa
 // Since this struct is returned in `list_channels` methods, expose it here in case users want to
 // construct one themselves.
 use crate::ln::{inbound_payment, ChannelId, PaymentHash, PaymentPreimage, PaymentSecret};
-use crate::ln::channel::{Channel, ChannelPhase, ChannelContext, ChannelError, ChannelUpdateStatus, ShutdownResult, UnfundedChannelContext, UpdateFulfillCommitFetch, OutboundV1Channel, InboundV1Channel, WithChannelContext};
+use crate::ln::channel::{self, Channel, ChannelPhase, ChannelContext, ChannelError, ChannelUpdateStatus, ShutdownResult, UnfundedChannelContext, UpdateFulfillCommitFetch, OutboundV1Channel, InboundV1Channel, WithChannelContext};
 use crate::ln::features::{Bolt12InvoiceFeatures, ChannelFeatures, ChannelTypeFeatures, InitFeatures, NodeFeatures};
 #[cfg(any(feature = "_test_utils", test))]
 use crate::ln::features::Bolt11InvoiceFeatures;
@@ -6176,7 +6176,7 @@ where
 				counterparty_node_id: counterparty_node_id.clone(),
 				funding_satoshis: msg.funding_satoshis,
 				push_msat: msg.push_msat,
-				channel_type: msg.channel_type.clone().unwrap(),
+				channel_type: channel::channel_type_from_open_channel(&msg),
 			}, None));
 			peer_state.inbound_channel_request_by_id.insert(channel_id, InboundChannelRequest {
 				open_channel_msg: msg.clone(),