Account for missing refund_onchain_address field

We allow de/serializing if the field is absent.

Author: tnull

src/lsps1/msgs.rs

@@ -108,6 +108,8 @@ pub struct OrderParameters {
 	/// May contain arbitrary associated data like a coupon code or a authentication token.
 	pub token: Option<String>,
 	/// The address where the LSP will send the funds if the order fails.
+	#[serde(default)]
+	#[serde(skip_serializing_if = "Option::is_none")]
 	#[serde(with = "unchecked_address_option")]
 	pub refund_onchain_address: Option<Address>,
 	/// Indicates if the channel should be announced to the network.