fix loading to use and return layer tree

fcore/browse-mode.sml

@@ -161,7 +161,5 @@ struct
     | FILE_BROWSER_AND_PATH {fileBrowser, path} =>
         handleFileBrowserAndPathInBrowseMode (model, fileBrowser, path)
     | SQUARES_LOAD_ERROR => CommonUpdate.squaresLoadError model
-    | USE_SQUARES squares =>
-        CommonUpdate.useSquaresInNormalMode (model, squares)
     | _ => (model, [])
 end