Fix warning

src/rc.ml

@@ -150,7 +150,7 @@ let object_of_entry object_common_tags entry = object
 end;;
 let object_of_setting setting = failwith "TODO";;
 
-let init ?(rc=(!Const.rc_file)) =
+let init ?(rc=(!Const.rc_file)) () =
   let basic_rc = get_basic (Lazy.force rc) in
   let common_tags = object_of_tag_list basic_rc.common_tags in
 object (self)

src/rc.mli

@@ -70,7 +70,7 @@ val object_of_entry :
   'a list -> basic_entry -> < command : string; tags : 'a list >
 val object_of_setting : 'a -> 'b
 val init :
-  ?rc:string lazy_t ->
+  ?rc:string lazy_t -> unit ->
   (< add_common_tags : 'b list -> 'a;
      add_entries : < command : string; tags : 'c list > list -> 'a;
      add_settings : 'd list -> 'a;