we expect unspent outputs but play it safe (#517)

impls/src/node_clients/http.rs

@@ -321,7 +321,8 @@ impl NodeClient for HTTPNodeClient {
 
 		let params = json!([start_index, end_index, max_outputs, Some(true)]);
 		let res = self.send_json_request::<OutputListing>("get_unspent_outputs", &params)?;
-		for out in res.outputs {
+		// We asked for unspent outputs via the api but defensively filter out spent outputs just in case.
+		for out in res.outputs.into_iter().filter(|out| out.spent == false) {
 			let is_coinbase = match out.output_type {
 				api::OutputType::Coinbase => true,
 				api::OutputType::Transaction => false,