f: older Rust version CI fixes for the façade method

Author: arik-so

lightning/src/ln/onion_utils.rs

@@ -949,16 +949,16 @@ where
 		_ => unreachable!(),
 	};
 
-	let (outer_session_priv, inner_session_priv) = if path.has_trampoline_hops() {
+	let secondary_session_priv = path.has_trampoline_hops().then(|| {
 		// If we have Trampoline hops, the outer onion session_priv is a hash of the inner one.
 		let session_priv_hash = Sha256::hash(&primary_session_priv.secret_bytes()).to_byte_array();
-		(
-			&SecretKey::from_slice(&session_priv_hash[..]).expect("You broke SHA-256!"),
-			Some(primary_session_priv),
-		)
-	} else {
-		(primary_session_priv, None)
-	};
+		SecretKey::from_slice(&session_priv_hash[..]).expect("You broke SHA-256!")
+	});
+
+	// the outer onion's session priv is the secondary (if it's set), or the primary as its fallback
+	let outer_session_priv = secondary_session_priv.as_ref().unwrap_or(primary_session_priv);
+	// the inner onion's session priv is only set if there is a secondary
+	let inner_session_priv = secondary_session_priv.as_ref().map(|_| primary_session_priv);
 
 	process_onion_failure_inner(
 		secp_ctx,