Gtk-Message: GtkDialog mapped without a transient parent

I installed orca 1.3.1 on my RStudio docker (Debian GNU/Linux 9 (stretch)). I am unable to export the image and I keep getting a warning related to Fontconfig + GTK-Message that I don't know if they are related to the issue or not.

sessionInfo()
R version 3.5.3 (2019-03-11)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 9 (stretch)

other attached packages:
[1] webshot_0.5.1 plotly_4.9.2.1 ggplot2_3.3.0 processx_3.4.2

I created a simple plot and when calling orca(),

> today <- Sys.Date()
> tm <- seq(0, 2, by = 1)
> x <- today - tm
> y <- rnorm(length(x))
> fig <- plot_ly(x = ~x, y = ~y, mode = 'lines', text = paste(tm, "days from today"))
> orca(fig, "foo.svg") # No error message but never finish
Unknown element "blank"tc/fonts/fonts.conf", line 100: 
Unable to revert mtime: /usr/local/share/fonts
Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
/

What's interesting is that I tried to create another simple figure from a terminal and it did created a png file although the name of the output file is different.

root@ae51f6d6054c:/home/rstudio/doodle# orca graph '{ "data": [{"y": [1,2,1]}] }' -o foo.png
Fontconfig warning: "/etc/fonts/fonts.conf", line 100: unknown element "blank"

done with code 1 in 164.75 ms - failed or incomplete task(s)
root@ae51f6d6054c:/home/rstudio/doodle# ls foo_1.png 
foo_1.png

Start with the R orca() call and the equivalent orca graph CLI invocation described in the issue, comparing their output filenames, exit status, and completion behavior. Check how the Fontconfig and GTK warnings relate to the failed export; done means the requested image export completes successfully without an incomplete task.