While Compiling Vaadin Theme Showing the Error

While compiling Vaadin theme it is showing the error:

select a theme file (.scss) or a vaadin project to compile
`@import "addons.scss";
@import "../ftpcapp/ftpcapp";
@import "../valo/valo";
@import "../ftpcapp/custom";
@import "AppTheme.scss";
@include variables($background18, $app18, black);
@include settings($app18, $background18);

.ftpcapp18 {
  @include addons;
  @include valo;
  @include themeitems($app18, $button-color18);
  @include ftpcapp;
  @include AppTheme;
  @include custom;
}