f actually declare a variable for legacy fields so it can be read

Author: TheBlueMatt

lightning/src/util/ser_macros.rs

@@ -818,6 +818,9 @@ macro_rules! _init_tlv_based_struct_field {
 	($field: ident, option) => {
 		$field
 	};
+	($field: ident, (legacy, $fieldty: ty, $read: expr, $write: expr)) => {
+		$crate::_init_tlv_based_struct_field!($field, option)
+	};
 	($field: ident, (option: $trait: ident $(, $read_arg: expr)?)) => {
 		$crate::_init_tlv_based_struct_field!($field, option)
 	};