Fix unexpected error with wallet power updates

If the power state is updated in the wallet before any Transaction activity occurs there are no subscribers to the broadcast channel which produced an incorrect error.

This PR logs the event but does not send it back across the FFI as an error.

base_layer/wallet/src/transaction_service/service.rs

@@ -1228,9 +1228,13 @@ where
             PowerMode::Low => self.config.low_power_polling_timeout,
             PowerMode::Normal => self.config.base_node_monitoring_timeout,
         };
-        self.timeout_update_publisher
-            .send(timeout)
-            .map_err(|_| TransactionServiceError::ProtocolChannelError)?;
+        if let Err(e) = self.timeout_update_publisher.send(timeout) {
+            trace!(
+                target: LOG_TARGET,
+                "Could not send Timeout update, no subscribers to receive. (Err {:?})",
+                e
+            );
+        }
 
         Ok(())
     }

base_layer/wallet/tests/transaction_service/service.rs

@@ -1813,6 +1813,9 @@ fn transaction_base_node_monitoring() {
     let (_, _, bob_outbound_service, mut bob_tx_sender, _, _, _, _) =
         setup_transaction_service_no_comms(&mut runtime, factories.clone(), TransactionMemoryDatabase::new(), None);
 
+    runtime.block_on(alice_ts.set_low_power_mode()).unwrap();
+    runtime.block_on(alice_ts.set_normal_power_mode()).unwrap();
+
     let mut alice_total_available = 250000 * uT;
     let (_utxo, uo) = make_input(&mut OsRng, alice_total_available, &factories.commitment);
     runtime.block_on(alice_output_manager.add_output(uo)).unwrap();