Check value balance during IBC packet timeout (#3903)

Once the mock test framework is further along, it would be good to add
some tests around this logic.

Closes #3773

crates/core/component/shielded-pool/src/component/transfer.rs

@@ -261,7 +261,7 @@ async fn recv_transfer_packet_inner<S: StateWrite>(
     //
     // https://github.com/cosmos/ibc/tree/main/spec/app/ics-020-fungible-token-transfer (onRecvPacket)
     //
-    // NOTE: spec says proto but thsi is actualy JSON according to the ibc-go implementation
+    // NOTE: spec says proto but this is actually JSON according to the ibc-go implementation
     let packet_data: FungibleTokenPacketData = serde_json::from_slice(msg.packet.data.as_slice())
         .with_context(|| "failed to decode FTPD packet")?;
     let denom: asset::Metadata = packet_data
@@ -355,7 +355,6 @@ async fn recv_transfer_packet_inner<S: StateWrite>(
         // prefixedDenomination = prefix + data.denom
         //
         // then mint that denom to packet_data.receiver in packet_data.amount
-        // no value balance to update here since this is an exogenous denom
         let prefixed_denomination = format!(
             "{}/{}/{}",
             msg.packet.port_on_b, msg.packet.chan_on_b, packet_data.denom
@@ -478,6 +477,14 @@ async fn timeout_packet_inner<S: StateWrite>(mut state: S, msg: &MsgTimeout) ->
             new_value_balance,
         );
     } else {
+        let value_balance: Amount = state
+            .get(&state_key::ics20_value_balance(
+                &msg.packet.chan_on_a,
+                &denom.id(),
+            ))
+            .await?
+            .unwrap_or_else(Amount::zero);
+
         state
             .mint_note(
                 value,
@@ -491,6 +498,12 @@ async fn timeout_packet_inner<S: StateWrite>(mut state: S, msg: &MsgTimeout) ->
             )
             .await
             .context("failed to mint return voucher in ics20 transfer timeout")?;
+
+        let new_value_balance = value_balance.saturating_add(&value.amount);
+        state.put(
+            state_key::ics20_value_balance(&msg.packet.chan_on_a, &denom.id()),
+            new_value_balance,
+        );
     }
 
     Ok(())