test fails: kwb.plot::preview_themes()

[mrustl]

== Failed tests ================================================================
-- Error (test-demo.R:12:3): preview_themes() works ----------------------------
Error: Error: no applicable method for 'element_grob' applied to an object of class "NULL"
Backtrace:
     x
  1. \-kwb.plot::preview_themes() test-demo.R:12:2
  2.   \-kwb.plot::arrange_in_pdf(plots, landscape = landscape, ...)
  3.     +-base::do.call(gridExtra::grid.arrange, c(plots, list(...)))
  4.     \-(function (..., newpage = TRUE) ...
  5.       \-gridExtra::arrangeGrob(...)
  6.         \-base::lapply(grobs[toconv], ggplot2::ggplotGrob)
  7.           \-ggplot2:::FUN(X[[i]], ...)
  8.             +-ggplot2::ggplot_gtable(ggplot_build(x))
  9.             \-ggplot2:::ggplot_gtable.ggplot_built(ggplot_build(x))
 10.               \-layout$render(geom_grobs, data, theme, plot$labels)
 11.                 \-ggplot2:::f(..., self = self)
 12.                   \-self$facet$draw_panels(...)
 13.                     \-ggplot2:::f(...)
 14.                       \-coord$render_axis_h(range, theme)
 15.                         \-ggplot2:::f(...)
 16.                           \-ggplot2:::panel_guides_grob(...)
 17.                             +-ggplot2::guide_gengrob(guide, theme)
 18.                             \-ggplot2:::guide_gengrob.axis(guide, theme)
 19.                               \-ggplot2:::draw_axis(...)
 20.                                 +-rlang::exec(...)
 21.                                 \-(function (element, ...) ...

[ FAIL 1 | WARN 0 | SKIP 21 | PASS 31 ]
Error: Error: Test failures

https://github.com/KWB-R/kwb.plot/pull/2/checks?check_run_id=1921555257#step:9:235