Problem with example

[mtopart]

Hi,
When I try to run the examples, I get this error message.
What should I do ?
Thanks in advance

  s <- sticker(~plot(cars, cex=.5, cex.axis=.5, mgp=c(0,.3,0), xlab="", ylab=""),
+              package="hexSticker", p_size=20, s_x=.8, s_y=.6, s_width=1.4, s_height=1.2,
+              filename="inst/figures/baseplot.png")
Error in UseMethod("validGrob") : 
  no applicable method for 'validGrob' applied to an object of class "NULL"
In addition: Warning messages:
1: Using ragg device as default. Ignoring `type` and `antialias` arguments 
2: In editThisGrob(grob, specs) : slot 'vp' not found
3: In editThisGrob(grob, specs) : slot 'name' not found 

[tentacles-from-outer-space]

Second on this.

When i run an example first time it is ok. Running it second time (no changes) show the error:

library(hexSticker)
#> Warning: package 'hexSticker' was built under R version 4.1.3
library(ggplot2)

outfile <- tempfile(fileext=".png")
s <- sticker(~plot(cars, cex=.5, cex.axis=.5, mgp=c(0,.3,0), xlab="", ylab=""),
             package="X", p_size=20, s_x=.8, s_y=.6, s_width=1.4, s_height=1.2,
             filename=outfile)
#> Warning: Using ragg device as default. Ignoring `type` and `antialias` arguments

outfile <- tempfile(fileext=".png")
s <- sticker(~plot(cars, cex=.5, cex.axis=.5, mgp=c(0,.3,0), xlab="", ylab=""),
             package="X", p_size=20, s_x=.8, s_y=.6, s_width=1.4, s_height=1.2,
             filename=outfile)
#> Warning: Using ragg device as default. Ignoring `type` and `antialias` arguments
#> Warning in editThisGrob(grob, specs): slot 'vp' not found
#> Warning in editThisGrob(grob, specs): slot 'name' not found
#> Error in UseMethod("validGrob"): no applicable method for 'validGrob' applied to an object of class "NULL"

^{Created on 2022-06-15 by the reprex package (v2.0.1)}

Problem is only with base graph. lattice/ggplot2 works.