[hxb] Fix mismatch between preview1 / pre #12351 nightlies and post #12351 nightlies

src/compiler/hxb/hxbReader.ml

@@ -1584,10 +1584,11 @@ class hxb_reader
 		a.a_write <- self#read_option (fun () -> self#read_field_ref);
 		a.a_call <- self#read_option (fun () -> self#read_field_ref);
 		a.a_constructor <- self#read_option (fun () -> self#read_field_ref);
-		a.a_default <- self#read_option (fun () -> 
-			let fctx = self#start_texpr in
-			let e = self#read_texpr fctx in
-			Lazy.from_val e);
+		if hxb_minor >= 1 then
+			a.a_default <- self#read_option (fun () ->
+				let fctx = self#start_texpr in
+				let e = self#read_texpr fctx in
+				Lazy.from_val e);
 
 		a.a_ops <- self#read_list (fun () ->
 			let i = read_byte ch in