Warning while publishing a shiny app

Has anyone got this error while publishing a Shiny app:

Warning in structure(if (i %in% npscales()) uniq(d[[i]]) else d[[i]], class = oldClass(x[[i]])) :

  Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.

  Consider 'structure(list(), *)' instead.

The same app works fine on another machine but throws error on a different machine.