default wrap to true in ppx_deriving_err_case

src/ppx/ppx_deriving_err_case.ml

@@ -98,9 +98,10 @@ let attribute_code ~code attrs =
   match c, code with Some c, _ | _, Some c -> c | _ -> 500
 
 let attribute_nowrap attrs =
-  List.find_map (fun a -> match a.attr_name.txt with
+  let wrap = List.find_map (fun a -> match a.attr_name.txt with
       | "nowrap" -> Some false
-      | _ -> None) attrs
+      | _ -> None) attrs in
+  Option.value ~default:true wrap
 
 let str_type_ext ~loc:_ ~path:_ t debug code =
   let loc = t.ptyext_loc in
@@ -111,7 +112,7 @@ let str_type_ext ~loc:_ ~path:_ t debug code =
       | Pext_decl ([], args, None) ->
         let code = attribute_code ~code pext.pext_attributes in
         let wrap = attribute_nowrap pext.pext_attributes in
-        let case = Encoding.resolve_case ~loc @@ Encoding.constructor_label ?wrap ~case:`snake
+        let case = Encoding.resolve_case ~loc @@ Encoding.constructor_label ~wrap ~case:`snake
             ~loc ~name:pext.pext_name.txt ~attrs:pext.pext_attributes args in
         let select = pext.pext_name.txt, (match args with Pcstr_tuple [] -> false | _ -> true) in
         Some (code, case, select)